Oppenheimer Short Duration Fund N-CSRS Certified semi-annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORMN-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT

INVESTMENT COMPANIES

Investment Company Act file number811-22520

Oppenheimer Ultra-Short Duration Fund

(Exact name of registrant as specified in charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of principal executive offices) (Zip code)

Cynthia Lo Bessette

OFI Global Asset Management, Inc.

225 Liberty Street, New York, New York 10281-1008

(Name and address of agent for service)

Registrant’s telephone number, including area code:(303)768-3200

Date of fiscal year end:July 31

Date of reporting period:1/31/2019

Item 1. Reports to Stockholders.

Important Notice: The Securities and Exchange Commission will permit funds to deliver shareholder reports electronically beginning January 1, 2021. At that time, OppenheimerFunds will send a notice, either by mail or email, each time your fund’s updated report is available on our website (oppenheimerfunds.com). Investors enrolled in electronic delivery will receive the notice by email, with links to the updated report. Investors who are not enrolled in electronic delivery by January 1, 2021 will receive the notice in the mail. All investors who prefer to receive shareholder reports in paper may, at any time, choose that option free of charge by calling 1.800.225.5677.

Important Updates

On October 18, 2018, Massachusetts Mutual Life Insurance Company, an indirect corporate parent of OppenheimerFunds, Inc. and its subsidiaries OFI Global Asset Management, Inc., OFI SteelPath, Inc. and OFI Advisors, LLC, announced that it has entered into an agreement whereby Invesco Ltd., a global investment management company, will acquire OppenheimerFunds, Inc. As of the date of this report, the transaction is expected to close in the second quarter of 2019, pending necessary regulatory and other third-party approvals. This is subject to change. See the Notes to Financial Statements for more information.

Update to Shareholder Report Document Delivery

Beginning January 1, 2021, OppenheimerFunds will send a notice, either by mail or email, each time your fund’s updated report is available on our website (oppenheimerfunds.com). Investors who are not enrolled in electronic delivery by January 1, 2021 will receive the notice in the mail. Enrolling in electronic delivery will enable you to receive a direct link to your full shareholder report the moment it becomes available, and limit the amount of mail you receive. All investors who prefer to receive shareholder reports in paper may, at any time, choose that option.

How do you update your delivery preferences?

If you own these shares through a financial intermediary, you may contact your financial intermediary.

If your accounts are held through OppenheimerFunds and you receive statements, confirms, and other documents directly from us, you can enroll in our eDocs Direct^SM service atoppenheimerfunds.com or by calling us. Once you’re enrolled, you’ll begin to receive email notifications of updated documents when they become available. If you have any questions, feel free to call us at1.800.225.5677.

Table of Contents    

Top Holdings and Allocations	4
Fund Expenses	7
Statement of Investments	9
Statement of Assets and Liabilities	16
Statement of Operations	17
Statements of Changes in Net Assets	18
Financial Highlights	19
Notes to Financial Statements	24
Board Approval of the Fund’s Investment Advisory and Sub-Advisory Agreements	38
Portfolio Proxy Voting Policies and Guidelines; Updates to Statement of Investments	41
Trustees and Officers	42
Privacy Notice	43

Class Y Shares    

AVERAGE ANNUAL TOTAL RETURNS AT 1/31/19    

	Class Y Shares of the Fund	ICE BofA Merrill Lynch 3-Month U.S. Treasury Bill  Index
6-Month	1.27%	1.10%
1-Year	2.30	1.95
5-Year	1.11	0.67
Since Inception (4/25/11)	0.93	0.46

Performance data quoted represents past performance, which does not guarantee future results. The investment return and principal value of an investment in the Fund will fluctuate so that an investor’s shares, when redeemed, may be worth more or less than their original cost. Current performance may be lower or higher than the performance quoted. Returns do not consider capital gains or income taxes on an individual’s investment. Returns for periods of less than one year are cumulative and not annualized. For performance data current to the most recentmonth-end, visit oppenheimerfunds.com or call 1.800.CALL OPP (225.5677). There is no sales charge for Class Y shares. See Fund prospectuses and summary prospectuses for more information on share classes and sales charges.

3        OPPENHEIMER ULTRA-SHORT DURATION FUND

Top Holdings and Allocations

PORTFOLIO ALLOCATION

Non-Convertible Corporate Bonds and Notes	50.4	%
Short-Term Notes	44.0
Asset-Backed Securities	5.6
Portfolio holdings and allocations are subject to change. Percentages are as of January 31, 2019, and are based on the total market value of investments.

For more current Fund holdings, please visit oppenheimerfunds.com.

4        OPPENHEIMER ULTRA-SHORT DURATION FUND

Share Class Performance

AVERAGE ANNUAL TOTAL RETURNS AS OF 1/31/19    

	Inception Date		6-Month			1-Year			5-Year			Since Inception
Class A (OSDAX)		4/25/11		1.23	%		2.22	%		1.04	%		0.83	%
Class I (OSDIX)		11/28/14		1.27			2.10			N/A			1.55
Class Y (OSDYX)		4/25/11		1.27			2.30			1.11			0.93

STANDARDIZED YIELDS
For the 30 Days Ended 1/31/19
Class A	2.73%
Class I	2.82
Class Y	2.82

UNSUBSIDIZED STANDARDIZED YIELDS
For the 30 Days Ended 1/31/19
Class A	2.68%
Class I	2.70
Class Y	2.68

Performance data quoted represents past performance, which does not guarantee future results. The investment return and principal value of an investment in the Fund will fluctuate so that an investor’s shares, when redeemed, may be worth more or less than their original cost. Current performance may be lower or higher than the performance quoted. Returns do not consider capital gains or income taxes on an individual’s investment. For performance data current to the most recentmonth-end, visit oppenheimerfunds.com or call 1.800.CALL OPP (225.5677). There is no sales charge for Class A, Class I and Class Y shares. Class A shares are not currently available for purchase. Returns for periods of less than one year are cumulative and not annualized. See Fund prospectuses and summary prospectuses for more information on share classes.

Standardized yield is based on anSEC-standardized formula designed to approximate the Fund’s annualized hypothetical current income from securities less expenses for the30-day period ended January 31, 2019 and that date’s net asset value (for all share classes). Each result is compounded semiannually and then annualized. Falling share prices will tend to artificially raise yields. The unsubsidized standardized yield is computed under anSEC-standardized formula based on net income earned for the30-day period ended January 31, 2019. The calculation excludes any expense reimbursements and thus may result in a lower yield.

The Fund’s performance is compared to the performance of the ICE Bank of America (BofA) Merrill Lynch3-month U.S. Treasury Bill Index, an index of short-term U.S. Government securities with a remaining term to final maturity of less than three months. The Index isunmanaged and cannot be purchased directly by investors. While index comparisons may be useful to provide a benchmark for the Fund’s performance, it must be noted that the Fund’s investments are not limited to the investments comprising theIndex. Index performance includes reinvestment of income, but does not reflect transaction costs, fees, expenses or taxes. Index performance is shown for illustrative purposes only as a benchmark for the Fund’s performance, and does not predict or depict performance of the Fund. The Fund’s performance reflects the effects of the Fund’s business and operating expenses.

Before investing in any of the Oppenheimer funds, investors should carefully consider a fund’s investment objectives, risks, charges and expenses. Fund

5       ��OPPENHEIMER ULTRA-SHORT DURATION FUND

prospectuses and summary prospectuses contain this and other information about the funds, and may be obtained by asking your financial advisor, visiting oppenheimerfunds.com, or calling 1.800.CALL OPP (225.5677). Read prospectuses and summary prospectuses carefully before investing.

Shares of Oppenheimer funds are not deposits or obligations of any bank, are not guaranteed by any bank, are not insured by the FDIC or any other agency, and involve investment risks, including the possible loss of the principal amount invested.

6        OPPENHEIMER ULTRA-SHORT DURATION FUND

Fund Expenses

Fund Expenses. As a shareholder of the Fund, you incur two types of costs: (1) transaction costs, which may include sales charges (loads) on purchase payments and/or contingent deferred sales charges on redemptions; and (2) ongoing costs, including management fees; distribution and service fees; and other Fund expenses. These examples are intended to help you understand your ongoing costs (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds.

The examples are based on an investment of $1,000.00 invested at the beginning of the period and held for the entire6-month period ended January 31, 2019.

Actual Expenses. The first section of the table provides information about actual account values and actual expenses. You may use the information in this section for the class of shares you hold, together with the amount you invested, to estimate the expense that you paid over the period. Simply divide your account value by $1,000.00 (for example, an $8,600.00 account value divided by $1,000.00 = 8.60), then multiply the result by the number in the first section under the heading entitled “Expenses Paid During 6 Months Ended January 31, 2019” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes.The second section of the table provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio for each class of shares, and an assumed rate of return of 5% per year for each class before expenses, which is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example for the class of shares you hold with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs, such asfront-end or contingent deferred sales charges (loads). Therefore, the “hypothetical” section of the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs were included, your costs would have been higher.

7        OPPENHEIMER ULTRA-SHORT DURATION FUND

Actual	Beginning         Account         Value         August 1, 2018			Ending Account Value January 31, 2019			Expenses Paid During 6 Months Ended January 31, 2019
Class A		$	1,000.00		$	1,012.30		$	1.68
Class I			1,000.00			1,012.70			1.27
Class Y			1,000.00			1,012.70			1.27
Hypothetical
(5% return before expenses)
Class A			1,000.00			1,023.54			1.68
Class I			1,000.00			1,023.95			1.28
Class Y			1,000.00			1,023.95			1.28

Expenses are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 184/365 (to reflect theone-half year period). Those annualized expense ratios, excluding indirect expenses from affiliated funds, based on the6-month period ended January 31, 2019 are as follows:

Class	Expense Ratios
Class A	0.33%
Class I	0.25
Class Y	0.25

The expense ratios reflect voluntary and/or contractual waivers and/or reimbursements of expenses by the Fund’s Manager. Some of these undertakings may be modified or terminated at any time, as indicated in the Fund’s prospectus. The “Financial Highlights” tables in the Fund’s financial statements, included in this report, also show the gross expense ratios, without such waivers or reimbursements and reduction to custodian expenses, if applicable.

8        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF INVESTMENTSJanuary 31, 2019 Unaudited    

	Principal Amount		Value
Asset-Backed Securities—5.6%
AmeriCredit Automobile Receivables Trust:
Series2018-1, Cl. A2A, 2.71%, 7/19/21	$	726,290	$                725,441
Series2018-2, Cl. A2A, 2.86%, 11/18/21		1,200,000	1,198,586
Series2018-3, Cl. A2A, 3.11%, 1/18/22		1,000,000	1,001,282
Capital Auto Receivables Asset Trust, Series2018-2, Cl. A2, 3.02%, 2/22/211		1,500,000	1,500,652
CarMax Auto Owner Trust, Series2018-2, Cl. A2, 2.73%, 8/16/21		2,005,873	2,002,761
Ford Credit Auto Lease Trust, Series2018-A, Cl. A2A, 2.71%, 12/15/20		1,860,078	1,857,419
Mercedes-Benz Auto Lease Trust, Series2019-A, Cl. A2, 3.01%, 2/16/21		1,000,000	1,000,587
Nissan Auto Lease Trust, Series2018-A, Cl. A2A, 3.03%, 2/16/21		2,150,000	2,151,477
Toyota Auto Receivables Owner Trust, Series2018-D, Cl. A2, 2.98%, 8/15/21		1,750,000	1,753,266
World Omni Auto Receivables Trust, Series2018-B, Cl. A2, 2.57%, 7/15/21		1,282,839	1,280,785
World Omni Automobile Lease Securitization Trust, Series2018-A, Cl. A2, 2.59%, 11/16/20		1,834,715	1,830,839
Total Asset-Backed Securities (Cost $16,308,839)			16,303,095
Corporate Bonds and Notes—50.2%
Consumer Discretionary—5.0%
Automobiles—5.0%
American Honda Finance Corp.:
2.768% [US0003M+15] Sr. Unsec. Nts., 11/13/192		1,000,000	1,000,036
3.875% Sr. Unsec. Nts., 9/21/201		1,000,000	1,014,068
BMW US Capital LLC:
2.984% [US0003M+37] Sr. Unsec. Nts., 8/14/201,2		1,500,000	1,493,720
3.10% Sr. Unsec. Nts., 4/12/211		500,000	498,756
3.207% [US0003M+41] Sr. Unsec. Nts., 4/12/211,2		2,000,000	1,989,965
3.25% Sr. Unsec. Nts., 8/14/201		1,000,000	1,006,812
Daimler Finance North America LLC:
3.10% Sr. Unsec. Nts., 5/4/201		1,000,000	999,103
3.288% [US0003M+55] Sr. Unsec. Nts., 5/4/211,2		1,900,000	1,888,504
Toyota Motor Corp., 3.183% Sr. Unsec. Nts., 7/20/21		2,000,000	2,015,544
Toyota Motor Credit Corp.:
2.20% Sr. Unsec. Nts., 1/10/20		1,500,000	1,492,505
3.033% [US0003M+26] Sr. Unsec. Nts., 4/17/202		1,000,000	1,001,452
			14,400,465
Consumer Staples—1.7%
Beverages—0.8%
Diageo Capital plc:
2.88% [US0003M+24] Sr. Unsec. Nts., 5/18/202		1,500,000	1,498,318
3.00% Sr. Unsec. Nts., 5/18/20		1,000,000	1,002,781
			2,501,099

9        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF INVESTMENTSUnaudited / Continued    

	Principal Amount		Value
Food Products—0.9%
Mondelez International, Inc., 3.00% Sr. Unsec. Nts., 5/7/20	$	2,500,000	$                2,506,155
Financials—36.0%
Capital Markets—2.7%
Goldman Sachs Bank USA (New York), 3.20% Sr. Unsec. Nts., 6/5/20		2,000,000	2,006,845
Morgan Stanley:
3.168% [US0003M+55] Sr. Unsec. Nts., 2/10/212		500,000	500,180
5.50% Sr. Unsec. Nts., 7/24/20		2,200,000	2,280,153
UBS AG (London), 3.347% [US0003M+58] Sr. Unsec. Nts., 6/8/201,2		1,000,000	1,002,959
UBS AG (Stamford CT), 2.35% Sr. Unsec. Nts., 3/26/20		2,000,000	1,990,801
			7,780,938
Commercial Banks—31.1%
ABN AMRO Bank NV:
2.65% Sr. Unsec. Nts., 1/19/211		2,000,000	1,981,962
3.171% [US0003M+41] Sr. Unsec. Nts., 1/19/211,2		2,000,000	1,995,500
Australia & New Zealand Banking Group Ltd.:
2.25% Sr. Unsec. Nts., 12/19/191		1,500,000	1,490,603
2.921% [US0003M+32] Sr. Unsec. Nts., 11/9/201,2		1,000,000	999,643
Bank of Montreal:
2.10% Sr. Unsec. Nts., 6/15/20		1,594,000	1,579,086
3.10% Sr. Unsec. Nts., 4/13/21		1,000,000	1,004,580
3.228% [US0003M+44] Sr. Unsec. Nts., 6/15/202		1,500,000	1,504,709
3.257% [US0003M+46] Sr. Unsec. Nts., 4/13/212		1,000,000	1,001,847
3.376% [US0003M+60] Sr. Unsec. Nts., 12/12/192		1,200,000	1,205,114
Bank of Nova Scotia (The), 3.438% [US0003M+66] Sr. Unsec.
Nts., 6/14/192		1,500,000	1,503,100
BB&T Corp., 2.15% Sr. Unsec. Nts., 2/1/21		800,000	788,023
Branch Banking & Trust Co., 3.237% [US0003M+45] Sr.
Unsec. Nts., 1/15/202		1,250,000	1,253,276
Citibank NA, 3.276% [US0003M+50] Sr. Unsec. Nts., 6/12/202		1,000,000	1,001,232
Cooperatieve Rabobank UA, 2.50% Sr. Unsec. Nts., 1/19/21		500,000	496,276
DNB Bank ASA:
2.125% Sr. Unsec. Nts., 10/2/201		2,000,000	1,968,723
3.167% [US0003M+37] Sr. Unsec. Nts., 10/2/201,2		3,000,000	3,002,345
HSBC Bank plc, 4.75% Sr. Unsec. Nts., 1/19/211		1,306,000	1,345,536
HSBC Holdings plc, 5.10% Sr. Unsec. Nts., 4/5/21		3,000,000	3,128,059
ING Bank NV, 3.226% [US0003M+61] Sr. Unsec. Nts., 8/15/191,2		1,250,000	1,252,334
JPMorgan Chase & Co.:
2.75% Sr. Unsec. Nts., 6/23/20		1,500,000	1,496,391
4.95% Sr. Unsec. Nts., 3/25/20		500,000	512,037
Lloyds Bank plc:
3.079% [US0003M+49] Sr. Unsec. Nts., 5/7/212		2,500,000	2,486,583
3.30% Sr. Unsec. Nts., 5/7/21		1,000,000	1,003,802

10        OPPENHEIMER ULTRA-SHORT DURATION FUND

	Principal Amount		Value
Commercial Banks (Continued)
Mizuho Financial Group, Inc., 2.632% Sr. Unsec. Nts., 4/12/211	$	4,071,000	$                4,017,435
MUFG Bank Ltd., 2.75% Sr. Unsec. Nts., 9/14/201		3,891,000	3,873,192
National Australia Bank Ltd.:
3.147% [US0003M+35] Sr. Unsec. Nts., 1/12/211,2		2,000,000	1,997,030
3.373% [US0003M+59] Sr. Unsec. Nts., 1/10/201,2		1,500,000	1,506,770
National Australia Bank Ltd. (New York), 2.50% Sr. Unsec. Nts., 1/12/21		1,500,000	1,484,152
National Bank of Canada:
3.336% [US0003M+56] Sr. Unsec. Nts., 6/12/202		2,000,000	2,007,193
3.373% [US0003M+60] Sr. Unsec. Nts., 1/17/202		2,000,000	2,008,044
Nordea Bank AB:
2.125% Sr. Unsec. Nts., 5/29/201		3,215,000	3,179,140
3.176% [US0003M+47] Sr. Unsec. Nts., 5/29/201,2		1,000,000	1,002,976
3.423% [US0003M+62] Sr. Unsec. Nts., 9/30/191,2		2,000,000	2,004,979
Royal Bank of Canada:
2.125% Sr. Unsec. Nts., 3/2/20		2,000,000	1,987,135
2.15% Sr. Unsec. Nts., 10/26/20		2,000,000	1,976,949
3.005% [US0003M+24] Sr. Unsec. Nts., 10/26/202		1,000,000	999,009
3.497% [US0003M+71] Sr. Unsec. Nts., 4/15/192		1,000,000	1,001,390
Skandinaviska Enskilda Banken AB:
3.07% [US0003M+43] Sr. Unsec. Nts., 5/17/211,2		3,400,000	3,392,387
3.25% Sr. Unsec. Nts., 5/17/211		1,500,000	1,506,735
3.349% [US0003M+57] Sr. Unsec. Nts., 9/13/191,2		1,000,000	1,003,005
Societe Generale SA, 2.50% Sr. Unsec. Nts., 4/8/211		1,500,000	1,476,963
Sumitomo Mitsui Banking Corp.:
2.45% Sr. Unsec. Nts., 1/16/20		1,300,000	1,294,595
2.514% Sr. Unsec. Nts., 1/17/20		1,263,000	1,259,162
2.65% Sr. Unsec. Nts., 7/23/20		1,500,000	1,491,846
3.09% [US0003M+31] Sr. Unsec. Nts., 10/18/192		1,000,000	999,515
Svenska Handelsbanken AB:
3.127% [US0003M+36] Sr. Unsec. Nts., 9/8/202		3,000,000	3,001,844
3.229% [US0003M+49] Sr. Unsec. Nts., 9/6/192		1,000,000	1,002,226
3.35% Sr. Unsec. Nts., 5/24/21		1,000,000	1,004,901
Swedbank AB, 2.65% Sr. Unsec. Nts., 3/10/211		2,000,000	1,981,544
Toronto-Dominion Bank (The):
2.55% Sr. Unsec. Nts., 1/25/21		1,000,000	994,440
3.00% Sr. Unsec. Nts., 6/11/20		1,000,000	1,002,826
US Bank NA (Cincinnati OH), 2.912% [US0003M+14] Sr. Unsec. Nts., 10/23/202		2,000,000	1,996,293
Westpac Banking Corp.:
2.65% Sr. Unsec. Nts., 1/25/21		1,500,000	1,493,759
2.896% [US0003M+28] Sr. Unsec. Nts., 5/15/202		1,500,000	1,500,652
3.05% Sr. Unsec. Nts., 5/15/20		1,000,000	1,002,436
			90,451,284
Consumer Finance—2.2%
American Express Co.:
2.20% Sr. Unsec. Nts., 10/30/20		1,500,000	1,482,845

11        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF INVESTMENTSUnaudited / Continued

	Principal Amount		Value
Consumer Finance (Continued)
American Express Co.: (Continued)
3.081% [US0003M+33] Sr. Unsec. Nts., 10/30/202	$	1,000,000	$                999,098
3.375% Sr. Unsec. Nts., 5/17/21		1,000,000	1,007,609
American Express Credit Corp., 3.068% [US0003M+33] Sr. Unsec. Nts., 5/3/192		1,000,000	1,000,327
Capital One Financial Corp., 3.201% [US0003M+45] Sr. Unsec. Nts., 10/30/202		2,000,000	1,987,438
			6,477,317
Health Care—0.7%
Pharmaceuticals—0.7%
Pfizer, Inc., 3.00% Sr. Unsec. Nts., 9/15/21		2,000,000	2,015,765
Industrials—3.6%
Aerospace & Defense—1.0%
General Dynamics Corp.:
2.875% Sr. Unsec. Nts., 5/11/20		2,000,000	2,004,526
2.998% [US0003M+38] Sr. Unsec. Nts., 5/11/212		1,000,000	1,001,028
			3,005,554
Industrial Conglomerates—0.4%
3M Co., 3.00% Sr. Unsec. Nts., 9/14/21		1,000,000	1,009,455
Machinery—2.2%
Caterpillar Financial Services Corp.:
2.95% Sr. Unsec. Nts., 5/15/20		1,000,000	1,002,514
3.018% [US0003M+23] Sr. Unsec. Nts., 3/15/212		1,500,000	1,492,224
John Deere Capital Corp.:
2.875% Sr. Unsec. Nts., 3/12/21		1,500,000	1,498,312
3.016% [US0003M+24] Sr. Unsec. Nts., 3/12/212		1,500,000	1,498,358
3.125% Sr. Unsec. Nts., 9/10/21		1,000,000	1,007,670
			6,499,078
Information Technology—1.7%
IT Services—1.7%
Western Union Co. (The), 3.453% [US0003M+80] Sr. Unsec. Nts., 5/22/192		4,800,000	4,803,468
Telecommunication Services—0.8%
Diversified Telecommunication Services—0.8%
Deutsche Telekom International Finance BV, 1.50% Sr. Unsec. Nts., 9/19/191		2,500,000	2,476,872
Utilities—0.7%
Electric Utilities—0.7%
Eversource Energy, 2.50% Sr. Unsec. Nts., 3/15/21		2,000,000	1,966,780
Total Corporate Bonds and Notes (Cost $145,781,915)			145,894,230

12        OPPENHEIMER ULTRA-SHORT DURATION FUND

	Principal Amount		Value
Short-Term Notes—43.9%
Aerospace & Defense—3.6%
Northrop Grumman Corp.:
2.876%, 2/13/191,3,4	$	1,400,000	$                1,398,592
3.104%, 4/17/191,3,4		3,600,000	3,576,873
United Technologies Corp., 2.866%, 2/27/191,3,4		5,400,000	5,388,510
			10,363,975
Auto Components—0.7%
Magna International, Inc., 2.783%, 2/14/191,3,4		2,000,000	1,997,830
Chemicals—5.0%
Air Liquide US LLC, 2.676%, 2/15/191,3,4		5,000,000	4,994,906
Cabot Corp.:
2.751%, 2/5/191,3,4		1,000,000	999,619
2.896%, 2/4/191,3,4		4,500,000	4,498,630
Eastman Chemical Co., 2.856%, 2/4/193,4		4,000,000	3,998,790
			14,491,945
Diversified Telecommunication Services—1.7%
AT&T, Inc.:
2.90%, 5/28/191,3,4		1,450,000	1,435,311
3.012%, 2/26/191,3,4		600,000	598,769
3.093%, 5/30/191,3,4		3,000,000	2,969,100
			5,003,180
Electric Utilities—5.7%
Alliant Energy Corp., 2.651%, 2/6/194		1,077,000	1,076,506
Commonwealth Edison Co., 2.806%, 2/14/193,4		3,000,000	2,996,745
Eversource Energy, 2.683%, 2/13/193,4		1,128,000	1,126,904
Nextera Energy Capital Holdings:
2.786%, 2/28/191,3,4		500,000	498,896
2.892%, 3/22/191,3,4		5,100,000	5,079,444
Southern Company Funding Corp., 2.825%, 2/20/193,4		5,500,000	5,491,389
			16,269,884
Energy Equipment & Services—4.3%
Schlumberger Holdings Corp.:
2.79%, 3/5/191,3,4		3,000,000	2,992,308
2.79%, 3/6/191,3,4		3,000,000	2,992,072
2.98%, 3/7/191,3,4		1,300,000	1,296,464
TransCanada PipeLine Ltd.:
2.745%, 2/22/191,3,4		600,000	598,965
3.072%, 4/4/191,3,4		2,000,000	1,989,644
3.124%, 4/2/191,3,4		3,000,000	2,984,974
			12,854,427
Food Products—0.9%
Mondelez International, Inc.:
3.076%, 3/5/193,4		820,000	817,857

13        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF INVESTMENTSUnaudited / Continued

	Principal Amount		Value
Food Products (Continued)
Mondelez International, Inc.: (Continued)
3.104%, 4/9/193,4	$	1,600,000	$	1,591,036
				2,408,893
Health Care Providers & Services—1.9%
Mckesson Corp., 2.856%, 2/25/191,3,4		5,500,000		5,489,183
Hotels, Restaurants & Leisure—1.7%
Marriot International, Inc.:
2.816%, 2/11/191,3,4		1,350,000		1,348,855
2.877%, 2/14/191,3,4		3,600,000		3,596,084
				4,944,939
Household Durables—5.2%
Leggett & Platt, Inc.:
2.733%, 2/13/191,3,4		1,700,000		1,698,287
2.869%, 2/15/191,3,4		4,000,000		3,995,325
Magna International, Inc., 2.907%, 2/7/191,3,4		3,700,000		3,698,018
Mohawk Industries, Inc.:
2.807%, 3/4/191,3,4		3,000,000		2,992,403
2.968%, 2/4/191,3,4		2,700,000		2,699,183
				15,083,216
Industrial Conglomerates—1.6%
Johnson Controls International plc, 2.782%, 2/5/191,3,4		4,700,000		4,698,218
Leasing & Factoring—1.9%
Hitachi Capital America Corp.:
2.856%, 2/26/194		500,000		498,977
2.897%, 2/27/194		5,000,000		4,989,361
				5,488,338
Metals & Mining—1.9%
Glencore Funding:
2.965%, 2/19/193,4		700,000		698,987
3.126%, 3/8/193,4		4,000,000		3,988,860
3.226%, 4/8/193,4		1,000,000		994,607
				5,682,454
Oil, Gas & Consumable Fuels—1.7%
ENI Finance USA, Inc.:
2.992%, 4/29/193,4		3,000,000		2,978,953
3.033%, 4/10/193,4		2,000,000		1,989,167
				4,968,120
Personal Products—0.1%
Reckitt Benckiser Treasury Services plc, 2.824%, 2/4/193,4		200,000		199,947

14        OPPENHEIMER ULTRA-SHORT DURATION FUND

	Principal Amount			Value
Telephone Utilities—3.6%
Bell Canada, Inc.:
2.74%, 2/15/193,4	$	1,000,000		$	998,873
2.926%, 4/8/193,4		4,400,000			4,376,899
Telus Corp.:
3.011%, 3/1/191,4		1,400,000			1,396,795
3.013%, 5/1/191,4		4,000,000			3,970,050
					10,742,617
Tobacco—1.7%
BAT International Finance plc, 2.857%, 2/26/193,4		5,000,000			4,989,766
Transportation Infrastructure—0.7%
Ryder System, Inc., 2.732%, 2/11/194		1,893,000			1,891,395
Total Short-Term Notes (Cost $127,573,800)					127,568,327
Total Investments, at Value (Cost $289,664,554)		99.7	%		289,765,652
Net Other Assets (Liabilities)		0.3			972,294
Net Assets		100.0	%	$	290,737,946

Footnotes to Statement of Investments

1. Represents securities sold under Rule 144A, which are exempt from registration under the Securities Act of 1933, as amended. These securities have been determined to be liquid under guidelines established by the Board of Trustees. These securities amount to $136,723,521 or 47.03% of the Fund’s net assets at period end.

2. Represents the current interest rate for a variable or increasing rate security, determined as [Referenced Rate + Basis-point spread].

3. Security issued in an exempt transaction without registration under the Securities Act of 1933. Such securities amount to $113,745,243 or 39.12% of the Fund’s net assets, and have been determined to be liquid pursuant to guidelines adopted by the Board of Trustees.

4. Current yield as of period end.

Futures Contracts as of January 31, 2019

Description	Buy/Sell	Expiration Date	Number of Contracts	Notional Amount (000’s)	Value	Unrealized Appreciation/ (Depreciation)
United States Treasury Nts., 2 yr.	Sell	3/29/19	255	USD 53,669	$    54,143,672	$            (474,528)

Glossary:
Definitions
ICE LIBOR	Intercontinental Exchange London Interbank Offered Rate
US0003M	ICE LIBOR USD 3 Month

See accompanying Notes to Financial Statements.

15        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF ASSETS AND LIABILITIESJanuary 31, 2019 Unaudited

Assets
Investments, at value (cost $289,664,554)—see accompanying statement of investments	$	289,765,652
Cash		108,878
Cash used for collateral on futures		231,750
Receivables and other assets:
Interest		827,835
Shares of beneficial interest sold		25,016
Other		55,511
Total assets		291,014,642
Liabilities
Payables and other liabilities:
Shares of beneficial interest redeemed		128,963
Variation margin payable		61,758
Trustees’ compensation		37,444
Dividends		15,637
Shareholder communications		2,266
Other		30,628
Total liabilities		276,696
Net Assets	$	290,737,946
Composition of Net Assets
Par value of shares of beneficial interest	$	58,166
Additionalpaid-in capital		292,561,244
Total accumulated loss		(1,881,464)
Net Assets	$	290,737,946
Net Asset Value Per Share
Class A Shares:
Net asset value and redemption price per share (based on net assets of $99,910 and 20,000 shares of beneficial interest outstanding)		$5.00
Class I Shares:
Net asset value, redemption price and offering price per share (based on net assets of $10,569,575 and 2,088,862 shares of beneficial interest outstanding)		$5.06
Class Y Shares:
Net asset value, redemption price and offering price per share (based on net assets of $280,068,461 and 56,057,204 shares of beneficial interest outstanding)		$5.00

See accompanying Notes to Financial Statements.    

16        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENT OF

OPERATIONSFor the Six Months Ended January 31, 2019 Unaudited

Investment Income
Interest	$	5,284,478
Expenses
Management fees		582,632
Transfer and shareholder servicing agent fees:
Class A		26
Class I		1,583
Class Y		94,441
Shareholder communications:
Class I		40
Class Y		7,851
Legal, auditing and other professional fees		37,315
Trustees’ compensation		12,120
Borrowing fees		6,036
Custodian fees and expenses		1,488
Other		5,608
Total expenses		749,140
Less waivers and reimbursements of expenses		(257,538)
Net expenses		491,602
Net Investment Income		4,792,876
Realized and Unrealized Gain (Loss)
Net realized gain (loss) on:
Investment transactions in unaffiliated companies		(1,123,889)
Futures contracts		103,807
Net realized loss		(1,020,082)
Net change in unrealized appreciation/(depreciation) on:
Investment transactions in unaffiliated companies		1,141,400
Futures contracts		(498,920)
Net change in unrealized appreciation/(depreciation)		642,480
Net Increase in Net Assets Resulting from Operations	$	4,415,274

See accompanying Notes to Financial Statements.    

17        OPPENHEIMER ULTRA-SHORT DURATION FUND

STATEMENTS OF CHANGES IN NET ASSETS

	Six Months Ended January 31, 2019 (Unaudited)		Year Ended July 31, 20181
Operations
Net investment income	$	4,792,876	$	12,377,012
Net realized loss		(1,020,082)		(460,264)
Net change in unrealized appreciation/(depreciation)		642,480		(1,711,744)
Net increase in net assets resulting from operations		4,415,274		10,205,004
Dividends and/or Distributions to Shareholders
Dividends and distributions declared:
Class A		(1,218)		(1,697)
Class I		(131,910)		(195,487)
Class Y		(4,659,583)		(12,193,178)
Total dividends and distributions declared		(4,792,711)		(12,390,362)
Beneficial Interest Transactions
Net increase (decrease) in net assets resulting from beneficial interest transactions:
Class A		—		—
Class I		144,474		344,717
Class Y		(100,945,703)		(379,951,203)
Total beneficial interest transactions		(100,801,229)		(379,606,486)
Net Assets
Total decrease		(101,178,666)		(381,791,844)
Beginning of period		391,916,612		773,708,456
End of period	$	290,737,946	$	391,916,612

1. Prior period amounts have been conformed to current year presentation. See Notes to Financial Statements, Note

2– New Accounting Pronouncements for further details.

See accompanying Notes to Financial Statements.

18        OPPENHEIMER ULTRA-SHORT DURATION FUND

FINANCIAL HIGHLIGHTS

Class A	Six Months Ended January 31, 2019 (Unaudited)		Year Ended July 31, 2018		Year Ended July 31, 2017		Year Ended July 31, 20161		Year Ended July 31, 20151		Year Ended July 31, 20141
Per Share Operating Data
Net asset value, beginning of period		$5.00		$5.01		$5.01		$5.00		$5.01		$5.00
Income (loss) from investment operations:
Net investment income2		0.06		0.08		0.06		0.04		0.02		0.01
Net realized and unrealized gain (loss)		0.00		(0.01)		0.003		0.01		(0.01)		0.01
Total from investment operations		0.06		0.07		0.06		0.05		0.01		0.02
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.06)		(0.08)		(0.06)		(0.04)		(0.02)		(0.01)
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.00)3		(0.00)3
Total dividends and/or distributions to shareholders		(0.06)		(0.08)		(0.06)		(0.04)		(0.02)		(0.01)
Net asset value, end of period		$5.00		$5.00		$5.01		$5.01		$5.00		$5.01
Total Return, at Net Asset Value4		1.23%		1.51%		1.12%		0.96%		0.21%		0.37%
Ratios/Supplemental Data
Net assets, end of period (in thousands)		$100		$100		$100		$100		$100		$100
Average net assets (in thousands)		$100		$100		$100		$100		$100		$100
Ratios to average net assets:5
Net investment income		2.39%		1.62%		1.11%		0.86%		0.29%		0.24%
Expenses excluding specific expenses listed below		0.38%		0.38%		0.38%		0.38%		0.38%		0.37%
Interest and fees from borrowings		0.00%6		0.00%6		0.00%6		0.00%6		0.00%6		0.00%
Total expenses		0.38%		0.38%		0.38%7		0.38%7		0.38%7		0.37%7
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.33%		0.33%		0.32%		0.33%		0.33%		0.32%
Portfolio turnover rate		34%		72%		52%		90%		106%		86%

19        OPPENHEIMER ULTRA-SHORT DURATION FUND

FINANCIAL HIGHLIGHTSContinued

1. On August 7, 2015, the Fund effected a share split as described in Note 11 of the accompanying Notes. Per share data prior to this date has been restated to give effect to the share split.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Less than $0.005 per share.

4. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

6. Less than 0.005%.

7. Total expenses including indirect expenses from affiliated fund fees and expenses were as follows:

Year Ended July 31, 2017	0.38	%
Year Ended July 31, 2016	0.38	%
Year Ended July 31, 2015	0.38	%
Year Ended July 31, 2014	0.37	%

See accompanying Notes to Financial Statements.

20        OPPENHEIMER ULTRA-SHORT DURATION FUND

Class I	Six Months Ended January 31, 2019 (Unaudited)		Year Ended July 31, 2018		Year Ended July 31, 2017		Year Ended July 31, 20161		Period Ended July 31, 20151,2
Per Share Operating Data
Net asset value, beginning of period		$5.06		$5.07		$5.01		$5.00		$5.01
Income (loss) from investment operations:
Net investment income3		0.06		0.08		0.06		0.05		0.02
Net realized and unrealized gain (loss)		0.00		(0.00)4		0.06		0.01		(0.01)
Total from investment operations		0.06		0.08		0.12		0.06		0.01
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.06)		(0.09)		(0.06)		(0.05)		(0.02)
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.00)4
Total dividends and/or distributions to shareholders		(0.06)		(0.09)		(0.06)		(0.05)		(0.02)
Net asset value, end of period		$5.06		$5.06		$5.07		$5.01		$5.00
Total Return, at Net Asset Value5		1.27%		1.58%		2.38%		1.04%		0.19%
Ratios/Supplemental Data
Net assets, end of period (in thousands)		$10,570		$10,426		$10,109		$13,789		$10
Average net assets (in thousands)		$10,473		$10,216		$8,238		$5,453		$10
Ratios to average net assets:6
Net investment income		2.47%		1.67%		1.21%		1.02%		0.42%
Expenses excluding specific expenses listed below		0.37%		0.40%		0.36%		0.37%		0.35%
Interest and fees from borrowings		0.00%7		0.00%7		0.00%7		0.00%7		0.00% 7
Total expenses		0.37%		0.40%		0.36%8		0.37%8		0.35% 8
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.25%		0.28%		0.25%		0.25%		0.25%
Portfolio turnover rate		34%		72%		52%		90%		106%

1. On August 7, 2015, the Fund effected a share split as described in Note 11 of the accompanying Notes. Per share data prior to this date has been restated to give effect to the share split.

2.For the period from November 28, 2014 (inception of offering) to July 31, 2015.

3.Per share amounts calculated based on the average shares outstanding during the period.

4.Less than $0.005 per share.

5. Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

6. Annualized for periods less than one full year.

7. Less than 0.005%.

8. Total expenses including indirect expenses from affiliated fund fees and expenses were as follows:

Year Ended July 31, 2017	0.36	%
Year Ended July 31, 2016	0.37	%
Period Ended July 31, 2015	0.35	%

See accompanying Notes to Financial Statements.

21        OPPENHEIMER ULTRA-SHORT DURATION FUND

FINANCIAL HIGHLIGHTSContinued

Class Y	Six Months Ended January 31, 2019 (Unaudited)		Year Ended July 31, 2018		Year Ended July 31, 2017		Year Ended July 31, 20161		Year Ended July 31, 20151		Year Ended July 31, 20141
Per Share Operating Data
Net asset value, beginning of period		$5.00		$5.01		$5.01		$5.00		$5.01		$5.01
Income (loss) from investment operations:
Net investment income2		0.06		0.08		0.06		0.05		0.02		0.02
Net realized and unrealized gain (loss)		0.00		(0.00)3		0.003		0.01		(0.01)		0.003
Total from investment operations		0.06		0.08		0.06		0.06		0.01		0.02
Dividends and/or distributions to shareholders:
Dividends from net investment income		(0.06)		(0.09)		(0.06)		(0.05)		(0.02)		(0.02)
Distributions from net realized gain		0.00		0.00		0.00		0.00		(0.00)3		(0.00)3
Total dividends and/or distributions to shareholders		(0.06)		(0.09)		(0.06)		(0.05)		(0.02)		(0.02)
Net asset value, end of period		$5.00		$5.00		$5.01		$5.01		$5.00		$5.01
Total Return, at Net Asset Value4		1.27%		1.58%		1.19%		1.05%		0.29%		0.34%
Ratios/Supplemental Data
Net assets, end of period (in thousands)		$280,068		$381,391		$763,499		$396,930		$276,780		$599,559
Average net assets (in thousands)		$374,161		$720,645		$501,550		$295,268		$431,806		$583,205
Ratios to average net assets:5
Net investment income		2.47%		1.69%		1.20%		0.94%		0.35%		0.31%
Expenses excluding specific expenses listed below		0.38%		0.38%		0.38%		0.39%		0.38%		0.38%
Interest and fees from borrowings		0.00%6		0.00%6		0.00%6		0.00%6		0.00%6		0.00%
Total expenses		0.38%		0.38%		0.38%7		0.39%7		0.38%7		0.38%7
Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses		0.25%		0.25%		0.25%		0.25%		0.25%		0.25%
Portfolio turnover rate		34%		72%		52%		90%		106%		86%

22        OPPENHEIMER ULTRA-SHORT DURATION FUND

1. On August 7, 2015, the Fund effected a share split as described in Note 11 of the accompanying Notes. Per share data prior to this date has been restated to give effect to the share split.

2. Per share amounts calculated based on the average shares outstanding during the period.

3. Less than $0.005 per share.

4.Assumes an initial investment on the business day before the first day of the fiscal period, with all dividends and distributions reinvested in additional shares on the reinvestment date, and redemption at the net asset value calculated on the last business day of the fiscal period. Sales charges are not reflected in the total returns. Total returns are not annualized for periods less than one full year. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

5. Annualized for periods less than one full year.

6. Less than 0.005%.

7.Total expenses including indirect expenses from affiliated fund fees and expenses were as follows:

Year Ended July 31, 2017	0.38	%
Year Ended July 31, 2016	0.39	%
Year Ended July 31, 2015	0.38	%
Year Ended July 31, 2014	0.38	%

See accompanying Notes to Financial Statements.

23        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSJanuary 31, 2019 Unaudited

1. Organization

Oppenheimer Ultra-Short Duration Fund (the “Fund”) is registered under the Investment Company Act of 1940 (“1940 Act”), as amended, as a diversifiedopen-end management investment company. The Fund’s investment objective is to seek income. The Fund’s investment adviser is OFI Global Asset Management, Inc. (“OFI Global” or the “Manager”), a wholly-owned subsidiary of OppenheimerFunds, Inc. (“OFI” or the“Sub-Adviser”). The Manager has entered into asub-advisory agreement with OFI.

The Fund offers Class A, Class I and Class Y shares. Class A shares are sold at their offering price, which is the net asset value per share without any initial sales charge. Class A shares are currently not available for purchase. Class I and Class Y shares are sold to certain institutional investors without afront-end sales charge, however, the intermediaries may impose charges on their accountholders who beneficially own Class I and Class Y shares. All classes of shares have identical rights and voting privileges with respect to the Fund in general and exclusive voting rights on matters that affect that class alone. Earnings, net assets and net asset value per share may differ due to each class having its own expenses, such as transfer and shareholder servicing agent fees and shareholder communications, directly attributable to that class.

The following is a summary of significant accounting policies followed in the Fund’s preparation of financial statements in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”).

2. Significant Accounting Policies

Security Valuation. All investments in securities are recorded at their estimated fair value, as described in Note 3.

Allocation of Income, Expenses, Gains and Losses.Income, expenses (other than those attributable to a specific class), gains and losses are allocated on a daily basis to each class of shares based upon the relative proportion of net assets represented by such class. Operating expenses directly attributable to a specific class are charged against the operations of that class.

Dividends and Distributions to Shareholders. Dividends and distributions to shareholders, which are determined in accordance with income tax regulations and may differ from U.S. GAAP, are recorded on theex-dividend date. Income distributions, if any, are declared daily and paid monthly. Capital gain distributions, if any, are declared and paid annually or at other times as determined necessary by the Manager.

The tax character of distributions is determined as of the Fund’s fiscal year end. Therefore, a portion of the Fund’s distributions made to shareholders prior to the Fund’s fiscal year end may ultimately be categorized as a tax return of capital.

Investment Income.Dividend income is recorded on theex-dividend date or uponex-dividend notification in the case of certain foreign dividends where theex-dividend date may

24        OPPENHEIMER ULTRA-SHORT DURATION FUND

2. Significant Accounting Policies (Continued)

have passed.Non-cash dividends included in dividend income, if any, are recorded at the fair value of the securities received. Withholding taxes on foreign dividends, if any, and capital gains taxes on foreign investments, if any, have been provided for in accordance with the Fund’s understanding of the applicable tax rules and regulations. Interest income, if any, is recognized on an accrual basis. Discount and premium, which are included in interest income on the Statement of Operations, are amortized or accreted daily.

Custodian Fees. “Custodian fees and expenses” in the Statement of Operations may include interest expense incurred by the Fund on any cash overdrafts of its custodian account during the period. Such cash overdrafts may result from the effects of failed trades in portfolio securities and from cash outflows resulting from unanticipated shareholder redemption activity. The Fund pays interest to its custodian on such cash overdraft at a rate equal to the Prime Rate plus 0.35%. The “Reduction to custodian expenses” line item, if applicable, represents earnings on cash balances maintained by the Fund during the period. Such interest expense and other custodian fees may be paid with these earnings.

Security Transactions. Security transactions are recorded on the trade date. Realized gains and losses on securities sold are determined on the basis of identified cost.

Indemnifications.The Fund’s organizational documents provide current and former Trustees and officers with a limited indemnification against liabilities arising in connection with the performance of their duties to the Fund. In the normal course of business, the Fund may also enter into contracts that provide general indemnifications. The Fund’s maximum exposure under these arrangements is unknown as this would be dependent on future claims that may be made against the Fund. The risk of material loss from such claims is considered remote.

Federal Taxes. The Fund intends to comply with provisions of the Internal Revenue Code applicable to regulated investment companies and to distribute substantially all of its investment company taxable income to shareholders. Therefore, no federal income or excise tax provision is required. The Fund files income tax returns in U.S. federal and applicable state jurisdictions. The statute of limitations on the Fund’s tax return filings generally remains open for the three preceding fiscal reporting period ends. The Fund has analyzed its tax positions for the fiscal year ended July 31, 2018, including open tax years, and does not believe there are any uncertain tax positions requiring recognition in the Fund’s financial statements.

During the fiscal year ended July 31, 2018, the Funddid not utilize anycapital loss carryforwards to offset capital gains realized in that fiscal year. Capital losses will be carried forward to future years if not offset by gains.

At period end, it is estimated that the capital loss carryforwards would be $1,521,599, which will not expire.The estimated capital loss carryforward represents the carryforward as of the end of the last fiscal year, increased or decreased by capital losses or gains realized in the first six months of the current fiscal year. During the reporting period, it is estimated that the Fund will not utilize any capital loss carryforward to offset realized capital gains.

25        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

2. Significant Accounting Policies (Continued)

Net investment income (loss) and net realized gain (loss) may differ for financial statement and tax purposes. The character of dividends and distributions made during the fiscal year from net investment income or net realized gains are determined in accordance with federal income tax requirements, which may differ from the character of net investment income or net realized gains presented in those financial statements in accordance with U.S. GAAP. Also, due to timing of dividends and distributions, the fiscal year in which amounts are distributed may differ from the fiscal year in which the income or net realized gain was recorded by the Fund.

The aggregate cost of securities and other investments and the composition of unrealized appreciation and depreciation of securities and other investments for federal income tax purposes at period end are noted in the following table. The primary difference between book and tax appreciation or depreciation of securities and other investments, if applicable, is attributable to the tax deferral of losses or tax realization of financial statement unrealized gain or loss.

Federal tax cost of securities	$	289,664,554
Federal tax cost of other investments		(53,669,144)
Total federal tax cost	$	235,995,410
Gross unrealized appreciation	$	382,796
Gross unrealized depreciation		(756,226)
Net unrealized depreciation	$	(373,430)

Use of Estimates. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates.

New Accounting Pronouncements. In March 2017, Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”), ASU2017-08. This provides guidance related to the amortization period for certain purchased callable debt securities held at a premium. The ASU is effective for annual periods beginning after December 15, 2018, and interim periods within those annual periods. The Manager has evaluated the impacts of these changes on the financial statements and there are no material impacts.

During August 2018, the Securities and Exchange Commission (the “SEC”) issued Final Rule ReleaseNo. 33-10532 (the “Rule”), Disclosure Update and Simplification. The rule amends certain financial statement disclosure requirements to conform to U.S. GAAP. The amendments to Rule6-04.17 of RegulationS-X (balance sheet) remove the requirement to separately state the book basis components of net assets: undistributed (over-distribution of) net investment income (“UNII”), accumulated undistributed net realized gains (losses), and net unrealized appreciation (depreciation) at the balance sheet date. Instead, consistent with U.S. GAAP, funds will be required to disclose total distributable earnings. The amendments to Rule6-09 of RegulationS-X (statement of changes in net assets) remove the requirement to

26        OPPENHEIMER ULTRA-SHORT DURATION FUND

2. Significant Accounting Policies (Continued)

separately state the sources of distributions paid. Instead, consistent with U.S. GAAP, funds will be required to disclose the total amount of distributions paid, except that any tax return of capital must be separately disclosed. The amendments also remove the requirement to parenthetically state the book basis amount of UNII on the statement of changes in net assets. The requirements of the Rule were effective November 5, 2018, and the Fund’s Statement of Assets and Liabilities and Statement of Changes in Net Assets for the current reporting period have been modified accordingly. In addition, certain amounts within the Fund’s Statement of Changes in Net Assets for the prior fiscal period have been modified to conform to the Rule.

3. Securities Valuation

The Fund calculates the net asset value of its shares as of 4:00 P.M. Eastern Time, on each day the New York Stock Exchange (the “Exchange” or “NYSE”) is open for trading, except in the case of a scheduled early closing of the Exchange, in which case the Fund will calculate net asset value of the shares as of the scheduled early closing time of the Exchange.

The Fund’s Board has adopted procedures for the valuation of the Fund’s securities and has delegated theday-to-day responsibility for valuation determinations under those procedures to the Manager. The Manager has established a Valuation Committee which is responsible for determining a fair valuation for any security for which market quotations are not readily available. The Valuation Committee’s fair valuation determinations are subject to review, approval and ratification by the Fund’s Board at least quarterly or more frequently, if necessary.

Valuation Methods and Inputs

Securities are valued primarily using unadjusted quoted market prices, when available, as supplied by third party pricing services or broker-dealers.

The following methodologies are used to determine the market value or the fair value of the types of securities described below:

Corporate and government debt securities (of U.S. or foreign issuers) and municipal debt securities, short-term notes, mortgage-backed securities, collateralized mortgage obligations, and asset-backed securities are valued at the mean between the bid and asked prices utilizing evaluated prices obtained from third party pricing services or broker-dealers who may use matrix pricing methods to determine the evaluated prices. Pricing services generally price debt securities assuming orderly transactions of an institutional “round lot” size, but some trades may occur in smaller, “odd lot” sizes, sometimes at lower prices than institutional round lot trades. Standard inputs generally considered by third-party pricing vendors include reported trade data, broker-dealer price quotations, benchmark yields, issuer spreads on comparable securities, the credit quality, yield, maturity, as well as other appropriate factors.

Futures contracts and futures options traded on a commodities or futures exchange will be valued at the final settlement price or official closing price on the principal exchange as reported by such principal exchange at its trading session ending at, or most recently prior to, the time when the Fund’s assets are valued.

27        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

3. Securities Valuation (Continued)

Securities for which market quotations are not readily available, or when a significant event has occurred that would materially affect the value of the security, are fair valued either (i) by a standardized fair valuation methodology applicable to the security type or the significant event as previously approved by the Valuation Committee and the Fund’s Board or (ii) as determined in good faith by the Manager’s Valuation Committee. The Valuation Committee considers all relevant facts that are reasonably available, through either public information or information available to the Manager, when determining the fair value of a security. Those standardized fair valuation methodologies include, but are not limited to, valuing securities at the last sale price or initially at cost and subsequently adjusting the value based on: changes in company specific fundamentals, changes in an appropriate securities index, or changes in the value of similar securities which may be further adjusted for any discounts related to security-specific resale restrictions. When possible, such methodologies use observable market inputs such as unadjusted quoted prices of similar securities, observable interest rates, currency rates and yield curves. The methodologies used for valuing securities are not necessarily an indication of the risks associated with investing in those securities nor can it be assured that the Fund can obtain the fair value assigned to a security if it were to sell the security.

Classifications

Each investment asset or liability of the Fund is assigned a level at measurement date based on the significance and source of the inputs to its valuation. Various data inputs may be used in determining the value of each of the Fund’s investments as of the reporting period end.

These data inputs are categorized in the following hierarchy under applicable financial accounting standards:

1) Level1-unadjusted quoted prices in active markets for identical assets or liabilities (including securities actively traded on a securities exchange)

2) Level2-inputs other than unadjusted quoted prices that are observable for the asset or liability (such as unadjusted quoted prices for similar assets and market corroborated inputs such as interest rates, prepayment speeds, credit risks, etc.)

3) Level3-significant unobservable inputs (including the Manager’s own judgments about assumptions that market participants would use in pricing the asset or liability).

The inputs used for valuing securities are not necessarily an indication of the risks associated with investing in those securities.

The table below categorizes amounts that are included in the Fund’s Statement of Assets and Liabilities at period end based on valuation input level:

28        OPPENHEIMER ULTRA-SHORT DURATION FUND

3. Securities Valuation (Continued)

	Level 1— Unadjusted Quoted Prices		Level 2— Other Significant Observable Inputs		Level 3— Significant Unobservable Inputs		Value
Assets Table
Investments, at Value:
Asset-Backed Securities	$	—	$	16,303,095	$	—	$	16,303,095
Corporate Bonds and Notes		—		145,894,230		—		145,894,230
Short-Term Notes		—		127,568,327		—		127,568,327
Total Assets	$	—	$	289,765,652	$	—	$	289,765,652
Liabilities Table
Other Financial Instruments:
Futures contracts	$	(474,528)	$	—	$	—	$	(474,528)
Total Liabilities	$	(474,528)	$	—	$	—	$	(474,528)

Forward currency exchange contracts and futures contracts, if any, are reported at their unrealized appreciation/depreciation at measurement date, which represents the change in the contract’s value from trade date. All additional assets and liabilities included in the above table are reported at their market value at measurement date.

For the reporting period, there were no transfers between levels.

4. Investments and Risks

Shareholder Concentration.At period end, one shareholder owned 20% or more of the Fund’s total outstanding shares.

The shareholder is a related partyof the Fund. Related parties may include, but are not limited to, the investment manager and its affiliates, affiliated broker dealers, fund of funds, and directors or employees.The related partyowned 88% of the Fund’s total outstanding shares at period end.

5. Market Risk Factors

The Fund’s investments in securities and/or financial derivatives may expose the Fund to various market risk factors:

Commodity Risk. Commodity risk relates to the change in value of commodities or commodity indexes as they relate to increases or decreases in the commodities market. Commodities are physical assets that have tangible properties. Examples of these types of assets are crude oil, heating oil, metals, livestock, and agricultural products.

Credit Risk.Credit risk relates to the ability of the issuer of debt to meet interest and principal payments, or both, as they come due. In general, lower-grade, higher-yield debt securities are subject to credit risk to a greater extent than lower-yield, higher-quality securities.

Equity Risk. Equity risk relates to the change in value of equity securities as they relate to increases or decreases in the general market.

Foreign Exchange Rate Risk. Foreign exchange rate risk relates to the change in the

29        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

5. Market Risk Factors (Continued)

U.S. dollar value of a security held that is denominated in a foreign currency. The U.S. dollar value of a foreign currency denominated security will decrease as the dollar appreciates against the currency, while the U.S. dollar value will increase as the dollar depreciates against the currency.

Interest Rate Risk.Interest rate risk refers to the fluctuations in value of fixed-income securities resulting from the inverse relationship between price and yield. For example, an increase in general interest rates will tend to reduce the market value of already issued fixed-income investments, and a decline in general interest rates will tend to increase their value. In addition, debt securities with longer maturities, which tend to have higher yields, are subject to potentially greater fluctuations in value from changes in interest rates than obligations with shorter maturities.

Volatility Risk.Volatility risk refers to the magnitude of the movement, but not the direction of the movement, in a financial instrument’s price over a defined time period. Large increases or decreases in a financial instrument’s price over a relative time period typically indicate greater volatility risk, while small increases or decreases in its price typically indicate lower volatility risk.

6. Use of Derivatives

The Fund’s investment objective not only permits the Fund to purchase investment securities, it also allows the Fund to enter into various types of derivatives contracts, including, but not limited to, futures contracts, forward currency exchange contracts, credit default swaps, interest rate swaps, total return swaps, variance swaps and purchased and written options. In doing so, the Fund will employ strategies in differing combinations to permit it to increase, decrease, or change the level or types of exposure to market risk factors. These instruments may allow the Fund to pursue its objectives more quickly and efficiently than if it were to make direct purchases or sales of securities capable of effecting a similar response to market factors. Such contracts may be entered into through a bilateralover-the-counter (“OTC”) transaction, or through a securities or futures exchange and cleared through a clearinghouse.

Derivatives may have little or no initial cash investment relative to their market value exposure and therefore can produce significant gains or losses in excess of their cost due to changes in the market risk factors and the overall market. This use of embedded leverage allows the Fund to increase its market value exposure relative to its net assets and can substantially increase the volatility of the Fund’s performance. In instances where the Fund is using derivatives to decrease, or hedge, exposures to market risk factors for securities held by the Fund, there are also risks that those derivatives may not perform as expected resulting in losses for the combined or hedged positions. Some derivatives have the potential for unlimited loss, regardless of the size of the Fund’s initial investment.

Additional associated risks from investing in derivatives also exist and potentially could have significant effects on the valuation of the derivative and the Fund. Typically, the associated risks are not the risks that the Fund is attempting to increase or decrease exposure to, per its investment objectives, but are the additional risks from investing in derivatives.

30        OPPENHEIMER ULTRA-SHORT DURATION FUND

6. Use of Derivatives (Continued)

Examples of these associated risks are liquidity risk, which is the risk that the Fund will not be able to sell the derivative in the open market in a timely manner, and counterparty credit risk, which is the risk that the counterparty will not fulfill its obligation to the Fund.

The Fund’s actual exposures to these market risk factors and associated risks during the period are discussed in further detail, by derivative type, below.

Futures Contracts

A futures contract is a commitment to buy or sell a specific amount of a commodity, financial instrument or currency at a negotiated price on a stipulated future date. The Fund may buy and sell futures contracts and may also buy or write put or call options on these futures contracts. Futures contracts and options thereon are generally entered into on a regulated futures exchange and cleared through a clearinghouse associated with the exchange.

Upon entering into a futures contract, the Fund is required to deposit either cash or securities (initial margin) in an amount equal to a certain percentage of the contract value in an account registered in the futures commission merchant’s name. Subsequent payments (variation margin) are paid to or from the futures commission merchant each day equal to the daily changes in the contract value. Such payments are recorded as unrealized gains and losses. Should the Fund fail to make requested variation margin payments, the futures commission merchant can gain access to the initial margin to satisfy the Fund’s payment obligations.

Futures contracts are reported on a schedule following the Statement of Investments. Securities held by a futures commission merchant to cover initial margin requirements on open futures contracts are noted in the Statement of Investments. Cash held by a futures commission merchant to cover initial margin requirements on open futures contracts and the receivable and/or payable for the daily mark to market for the variation margin are noted in the Statement of Assets and Liabilities. The net change in unrealized appreciation and depreciation is reported in the Statement of Operations. Realized gains (losses) are reported in the Statement of Operations at the closing or expiration of futures contracts.

The Fund may purchase and/or sell financial futures contracts and options on futures contracts to gain exposure to, or decrease exposure to interest rate risk, equity risk, foreign exchange rate risk, volatility risk, or commodity risk.

During the reporting period, the Fund had an ending monthly average market value of $75,012,244 on futures contracts sold.

Additional associated risks of entering into futures contracts (and related options) include the possibility that there may be an illiquid market where the Fund is unable to liquidate the contract or enter into an offsetting position and, if used for hedging purposes, the risk that the price of the contract will correlate imperfectly with the prices of the Fund’s securities.

Counterparty Credit Risk.Derivative positions are subject to the risk that the counterparty will not fulfill its obligation to the Fund. The Fund intends to enter into derivative transactions with counterparties that the Manager believes to be creditworthy at the time of the transaction.

31        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

6. Use of Derivatives (Continued)

For financial reporting purposes, the Fund does not offset derivative assets and derivative liabilities that are subject to netting arrangements in the Statement of Assets and Liabilities. Bankruptcy or insolvency laws of a particular jurisdiction may impose restrictions on or prohibitions against the right of offset in bankruptcy, insolvency or other events.

The Fund’s risk of loss from counterparty credit risk on exchange-traded derivatives cleared through a clearinghouse and for centrally cleared swaps is generally considered lower than as compared to OTC derivatives. However, counterparty credit risk exists with respect to initial and variation margin deposited/paid by the Fund that is held in futures commission merchant, broker and/or clearinghouse accounts for such exchange-traded derivatives and for centrally cleared swaps.

With respect to centrally cleared swaps, such transactions will be submitted for clearing, and if cleared, will be held in accounts at futures commission merchants or brokers that are members of clearinghouses. While brokers, futures commission merchants and clearinghouses are required to segregate customer margin from their own assets, in the event that a broker, futures commission merchant or clearinghouse becomes insolvent or goes into bankruptcy and at that time there is a shortfall in the aggregate amount of margin held by the broker, futures commission merchant or clearinghouse for all its customers, U.S. bankruptcy laws will typically allocate that shortfall on apro-rata basis across all the broker’s, futures commission merchant’s or clearinghouse’s customers, potentially resulting in losses to the Fund.

There is the risk that a broker, futures commission merchant or clearinghouse will decline to clear a transaction on the Fund’s behalf, and the Fund may be required to pay a termination fee to the executing broker with whom the Fund initially enters into the transaction. Clearinghouses may also be permitted to terminate centrally cleared swaps at any time. The Fund is also subject to the risk that the broker or futures commission merchant will improperly use the Fund’s assets deposited/paid as initial or variation margin to satisfy payment obligations of another customer. In the event of a default by another customer of the broker or futures commission merchant, the Fund might not receive its variation margin payments from the clearinghouse, due to the manner in which variation margin payments are aggregated for all customers of the broker/futures commission merchant.

Collateral and margin requirements differ by type of derivative. Margin requirements are established by the broker, futures commission merchant or clearinghouse for exchange-traded and cleared derivatives, including centrally cleared swaps. Brokers, futures commission merchants and clearinghouses can ask for margin in excess of the regulatory minimum, or increase the margin amount, in certain circumstances.

For financial reporting purposes, cash collateral that has been pledged to cover obligations of the Fund, if any, is reported separately on the Statement of Assets and Liabilities as cash pledged as collateral.Non-cash collateral pledged by the Fund, if any, is noted in the Statement of Investments. Generally, the amount of collateral due from or to a party must exceed a minimum transfer amount threshold (e.g., $250,000) before a transfer has to be made. To the extent amounts due to the Fund from its counterparties are not fully collateralized, contractually or otherwise, the Fund bears the risk of loss from counterparty nonperformance.

32        OPPENHEIMER ULTRA-SHORT DURATION FUND

6. Use of Derivatives (Continued)

The following table presents the valuations of derivative instruments by risk exposure as reported within the Statement of Assets and Liabilities at period end:

	Liability Derivatives
Derivatives Not Accounted for as Hedging Instruments	Statement of Assets     and Liabilities         Location	Value
Interest rate contracts	Variation margin payable		$            61,758*

*Includes only the current day’s variation margin. Prior variation margin movements have been reflected in cash on the Statement of Assets and Liabilities upon receipt or payment.

The effect of derivative instruments on the Statement of Operations is as follows:

Amount of Realized Gain or (Loss) Recognized on Derivatives
Derivatives Not Accounted for as Hedging Instruments	Futures   contracts
Interest rate contracts	$	103,807
Amount of Change in Unrealized Gain or (Loss) Recognized on Derivatives
Derivatives Not Accounted for as Hedging Instruments	Futures   contracts
Interest rate contracts	$	(498,920)

7. Shares of Beneficial Interest

The Fund has authorized an unlimited number of $0.001 par value shares of beneficial interest of each class. Transactions in shares of beneficial interest were as follows:

	Six Months Ended January 31, 2019				Year Ended July 31, 2018
	Shares		Amount		Shares		Amount
Class A
Sold		—	$	—		—	$	—
Dividends and/or distributions reinvested		—		—		—		—
Redeemed		—		—		—		—
Net increase		—	$	—		—	$	—
Class I
Sold		6,011	$	30,393		36,323	$	183,800
Dividends and/or distributions reinvested		26,061		131,781		35,634		180,425
Redeemed		(3,499)		(17,700)		(3,855)		(19,508)
Net increase		28,573	$	144,474		68,102	$	344,717

33        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

7. Shares of Beneficial Interest (Continued)    

	Six Months Ended January 31, 2019				Year Ended July 31, 2018
	Shares		Amount		Shares		Amount
Class Y
Sold		97,016,666	$	484,851,026		271,666,629	$	1,359,868,315
Dividends and/or distributions reinvested		932,206		4,657,957		2,430,597		12,162,533
Redeemed		(118,185,533)		(590,454,686)		(350,120,932)		(1,751,982,051)
Net decrease		(20,236,661)	$	(100,945,703)		(76,023,706)	$	(379,951,203)

8. Purchases and Sales of Securities

The aggregate cost of purchases and proceeds from sales of securities, other than short-term obligations, for the reporting period were as follows:

	Purchases		Sales
Investment securities	$	81,361,948	$	169,936,310

9. Fees and Other Transactions with Affiliates

Management Fees. Under the investment advisory agreement, the Fund pays the Manager a management fee based on the daily net assets of the Fund at an annual rate of 0.30%.

Sub-Adviser Fees.The Manager has retained theSub-Adviser to provide theday-to-day portfolio management of the Fund. Under theSub-Advisory Agreement, the Manager pays theSub-Adviser an annual fee in monthly installments, equal to a percentage of the investment management fee collected by the Manager from the Fund, which shall be calculated after any investment management fee waivers. The fee paid to theSub-Adviser is paid by the Manager, not by the Fund.

Transfer Agent Fees.OFI Global (the “Transfer Agent”) serves as the transfer and shareholder servicing agent for the Fund. The Fund pays the Transfer Agent a fee based on annual net assets, which shall be calculated after any applicable fee waivers. Fees incurred and average net assets for each class with respect to these services are detailed in the Statement of Operations and Financial Highlights, respectively.

Sub-Transfer Agent Fees.The Transfer Agent has retained Shareholder Services, Inc., a wholly-owned subsidiary of OFI (the“Sub-Transfer Agent”), to provide theday-to-day transfer agent and shareholder servicing of the Fund. Under theSub-Transfer Agency Agreement, the Transfer Agent pays theSub-Transfer Agent an annual fee in monthly installments, equal to a percentage of the transfer agent fee collected by the Transfer Agent from the Fund, which shall be calculated after any applicable fee waivers. The fee paid to theSub-Transfer Agent is paid by the Transfer Agent, not by the Fund.

Trustees’ Compensation.The Fund’s Board of Trustees (“Board”) has adopted a compensation deferral plan for Independent Trustees that enables Trustees to elect to defer receipt of all or a portion of the annual compensation they are entitled to receive from the

34        OPPENHEIMER ULTRA-SHORT DURATION FUND

9. Fees and Other Transactions with Affiliates (Continued)

Fund. For purposes of determining the amount owed to the Trustees under the plan, deferred amounts are treated as though equal dollar amounts had been invested in shares of the Fund or in other Oppenheimer funds selected by the Trustees. The Fund purchases shares of the funds selected for deferral by the Trustees in amounts equal to his or her deemed investment, resulting in a Fund asset equal to the deferred compensation liability. Such assets are included as a component of “Other” within the asset section of the Statement of Assets and Liabilities. Deferral of Trustees’ fees under the plan will not affect the net assets of the Fund and will not materially affect the Fund’s assets, liabilities or net investment income per share. Amounts will be deferred until distributed in accordance with the compensation deferral plan.

Service Plan for Class A Shares. The Fund has adopted a Service Plan (the “Plan”) for Class A shares pursuant to Rule12b-1 under the 1940 Act. Under the Plan, the Fund reimburses the Distributor for a portion of its costs incurred for services provided to accounts that hold Class A shares. Reimbursement is made periodically at an annual rate of up to

0.25% of the daily net assets of Class A shares of the Fund. The Distributor currently uses all of those fees to pay dealers, brokers, banks and other financial institutions periodically for providing personal service and maintenance of accounts of their customers that hold Class A shares. Any unreimbursed expenses the Distributor incurs with respect to Class A shares in any fiscal year cannot be recovered in subsequent periods. Fees incurred by the Fund under the Plan are detailed in the Statement of Operations. The Fund does not currently charge such fees on Class A shares.

Waivers and Reimbursements of Expenses. The Manager has contractually agreed to waive fees and/or reimburse expenses to limit the Fund’s “Expenses after payments, waivers and/or reimbursements and reduction to custodian expenses” (excluding any applicable dividend expense, taxes, interest and fees from borrowing, any subsidiary expenses, Acquired Fund Fees and Expenses, brokerage commissions, and certain other Fund expenses) so that, as percentages of average daily net assets, those expenses will not exceed the annual rate of 0.65% for Class A shares and 0.25% for Class I and Class Y shares, respectively. The Manager will also waive a portion of the advisory fee on Class A shares to the same extent that it waives any of the advisory fee on Class I or Class Y shares.

During the reporting period, the Manager waived fees and/or reimbursed the Fund as follows:

Class A	$26
Class I	5,911
Class Y	251,601

This fee waiver and/or expense reimbursement may not be amended or withdrawn for one year from the date of the Fund’s prospectus, unless approved by the Board.

35        OPPENHEIMER ULTRA-SHORT DURATION FUND

NOTES TO FINANCIAL STATEMENTSUnaudited / Continued

10. Borrowings and Other Financing

Joint Credit Facility.A number of mutual funds managed by the Manager participate in a $1.95 billion revolving credit facility (the “Facility”) intended to provide short-term financing, if necessary, subject to certain restrictions in connection with atypical redemption activity. Expenses and fees related to the Facility are paid by the participating funds and are disclosed separately or as other expenses on the Statement of Operations. The Fund did not utilize the Facility during the reporting period.

11. Share Split

As of the close of business on August 7, 2015, the Fund implemented a 2 for 1 share split. This share split effectively increased the number of outstanding shares for the Fund. As a result, shareholders’ accounts reflect additional shares with a lower net asset value per share. While the number of shares increased, neither the Fund’s holdings nor the total value of shareholders’ investments was affected. Per share data in the financial highlights prior to August 7, 2015, has been adjusted to give effect to this share split.

12. Pending Acquisition

On October 18, 2018, Massachusetts Mutual Life Insurance Company, an indirect corporate parent of theSub-Adviser and the Manager, announced that it has entered into an agreement whereby Invesco Ltd. (“Invesco”), a global investment management company, will acquire theSub-Adviser (the “Transaction”). In connection with the Transaction, on January 11, 2019, the Fund’s Board unanimously approved an Agreement and Plan of Reorganization (the “Agreement”), which provides for the transfer of the assets and liabilities of the Fund to a corresponding, newly formed fund (the “Acquiring Fund”) in the Invesco family of funds (the “Reorganization”) in exchange for shares of the corresponding Acquiring Fund of equal value to the value of the shares of the Fund as of the close of business on the closing date. Although the Acquiring Fund will be managed by Invesco Advisers, Inc., the Acquiring Fund will, as of the closing date, have the same investment objective and substantially similar principal investment strategies and risks as the Fund. After the Reorganization, Invesco Advisers, Inc. will be the investment adviser to the Acquiring Fund, and the Fund will be liquidated and dissolved under applicable law and terminate its registration under the Investment Company Act of 1940, as amended. The Reorganization is expected to be atax-free reorganization for U.S. federal income tax purposes.

The Reorganization is subject to the approval of shareholders of the Fund. Shareholders of record of the Fund on January 14, 2019 will be entitled to vote on the Reorganization and will receive a combined prospectus and proxy statement describing the Reorganization, the shareholder meeting, and a discussion of the factors the Fund’s Board considered in approving the Agreement. The combined prospectus and proxy statement is expected to be distributed to shareholders of record on or about February 28, 2019. The anticipated date of the shareholder meeting is on or about April 12, 2019.

36        OPPENHEIMER ULTRA-SHORT DURATION FUND

12. Pending Acquisition (Continued)

If shareholders approve the Agreement and certain other closing conditions are satisfied or waived, the Reorganization is expected to close during the second quarter of 2019, or as soon as practicable thereafter. This is subject to change.

37        OPPENHEIMER ULTRA-SHORT DURATION FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY

ANDSUB-ADVISORY AGREEMENTSUnaudited

The Fund has entered into an investment advisory agreement with OFI Global Asset Management, Inc. (“OFI Global” or the “Adviser”), a wholly-owned subsidiary of OppenheimerFunds, Inc. (“OFI” or the“Sub-Adviser”) (“OFI Global” and “OFI” together the “Managers”) and OFI Global has entered into asub-advisory agreement with OFI whereby OFI provides investmentsub-advisory services to the Fund (collectively, the “Agreements”). Each year, the Board of Trustees (the “Board”), including a majority of the independent Trustees, is required to determine whether to approve the terms of the Agreements and the renewal thereof. The Investment Company Act of 1940, as amended, requires that the Board request and evaluate, and that the Managers provide, such information as may be reasonably necessary to evaluate the terms of the Agreements. The Board employs an independent consultant to prepare a report that provides information, including comparative information that the Board requests for that purpose. In addition toin-person meetings focused on this evaluation, the Board receives information throughout the year regarding Fund services, fees, expenses and performance.

The Managers and the independent consultant provided information to the Board on the following factors: (i) the nature, quality and extent of the Managers’ services, (ii) the comparative investment performance of the Fund and the Managers, (iii) the fees and expenses of the Fund, including comparative fee and expense information, (iv) the profitability of the Managers and their affiliates, including an analysis of the cost of providing services, (v) whether economies of scale are realized as the Fund grows and whether fee levels reflect these economies of scale for Fund investors and (vi) other benefits to the Managers from their relationship with the Fund. The Board was aware that there are alternatives to retaining the Managers.

Outlined below is a summary of the principal information considered by the Board as well as the Board’s conclusions.

Nature, Quality and Extent of Services. The Board considered information about the nature, quality and extent of the services provided to the Fund and information regarding the Managers’ key personnel who provide such services. The Managers’ duties include providing the Fund with the services of theSub-Adviser’s portfolio managers and investment team, who provide research, analysis and other advisory services in regard to the Fund’s investments; and securities trading services. OFI Global is responsible for oversight of third-party service providers; monitoring compliance with applicable Fund policies and procedures and adherence to the Fund’s investment restrictions; risk management; and oversight of theSub-Adviser. OFI Global is also responsible for providing certain administrative services to the Fund. Those services include providing and supervising all administrative and clerical personnel who are necessary in order to provide effective corporate administration for the Fund; compiling and maintaining records with respect to the Fund’s operations; preparing and filing reports required by the U.S. Securities and Exchange Commission; preparing periodic reports regarding the operations of the Fund for its shareholders; preparing proxy materials for shareholder meetings; and preparing the registration statements required by federal and state securities laws for the sale of the Fund’s shares. OFI Global also provides the Fund with office space, facilities and equipment.

38        OPPENHEIMER ULTRA-SHORT DURATION FUND

The Board also considered the quality of the services provided and the quality of the Managers’ resources that are available to the Fund. The Board took account of the fact that theSub-Adviser has over fifty years of experience as an investment adviser and that its assets under management rank it among the top mutual fund managers in the United States. The Board evaluated the Managers’ advisory, administrative, accounting, legal, compliance and risk management services, among other services, and information the Board has received regarding the experience and professional qualifications of the Managers’ key personnel and the size and functions of their staff. In its evaluation of the quality of the portfolio management services provided, the Board considered the experience of Christopher Proctor and Adam Wilde the portfolio managers for the Fund, and theSub-Adviser’s investment team and analysts. The Board members also considered the totality of their experiences with the Managers as directors or trustees of the Fund and other funds advised by the Managers. The Board considered information regarding the quality of services provided by affiliates of the Managers, which the Board members have become knowledgeable about through their experiences with the Managers and in connection with the review or renewal of the Fund’s service agreements or service providers. The Board concluded, in light of the Managers’ experience, reputation, personnel, operations and resources that the Fund benefits from the services provided under the Agreements

Investment Performance of the Managers and the Fund. Throughout the year, the Managers provided information on the investment performance of the Fund, the Adviser and theSub-Adviser, including comparative performance information. The Board also reviewed information, prepared by the Managers and by the independent consultant, comparing the Fund’s historical performance to relevant market indices and to the performance of other ultrashort bond funds. The Board noted that the Fund performed generally in line with its category median for theone- and three-year periods, ranking in the 50th and 51st percentiles, respectively. It also noted that the Fund underperformed its category median for the five-year period, though it ranked in the 54th percentile of the category. The Board considered that the top performing funds in the category have generally achieved stronger yields by taking significantly more credit risk, as well as by investing further out on the yield curve, than the Fund.

Fees and Expenses of the Fund. The Board reviewed the fees paid to the Adviser and the other expenses borne by the Fund. The Board noted that the Adviser, not the Fund, pays theSub-Adviser’s fee under thesub-advisory agreement. The independent consultant provided comparative data in regard to the fees and expenses of the Fund and other ultrashort bond funds with comparable asset levels and distribution features. The Board noted that the Fund’s total expenses and its contractual management fee were lower than their respective peer group medians and category medians. The Board also considered that the Adviser has contractually agreed to waive fees and/or reimburse certain Fund expenses so that total expenses, as a percentage of average daily net assets, will not exceed the following annual rates: 0.65% for Class A shares and 0.25% for Class I shares and Class Y shares, and that the Adviser has agreed to waive a portion of the management fee on Class A shares to the same extent that it waives any of the management fee on Class I or Y shares as a result of this expense limitation. This expense limitation may not be amended

39        OPPENHEIMER ULTRA-SHORT DURATION FUND

BOARD APPROVAL OF THE FUND’S INVESTMENT ADVISORY

ANDSUB-ADVISORY AGREEMENTSUnaudited / Continued

or withdrawn for one year from the date of the Fund’s prospectus, unless approved by the Board. The Board also noted that the Adviser has voluntarily agreed to waive fees and/ or reimburse Fund expenses in an amount equal to the indirect management fees incurred through the Fund’s investments in funds managed by the Adviser or its affiliates.

Economies of Scale and Profits Realized by the Managers. The Board considered information regarding the Managers’ costs in serving as the Fund’s investment adviser andsub-adviser, including the costs associated with the personnel and systems necessary to manage the Fund, and information regarding the Managers’ profitability from their relationship with the Fund. The Board also considered that the Managers must be able to pay and retain experienced professional personnel at competitive rates to provide quality services to the Fund. The Board reviewed whether the Managers may realize economies of scale in managing and supporting the Fund and whether those economies of scale benefit the Fund’s shareholders at the current level of Fund assets in relation to its management fee. The Board noted that the Fund does not have management fee breakpoints at this time.

Other Benefits to the Managers. In addition to considering the profits realized by the Managers, the Board considered information that was provided regarding the direct and indirect benefits the Managers receive as a result of their relationship with the Fund, including compensation paid to the Managers’ affiliates.

Conclusions. These factors were also considered by the independent Trustees meeting separately from the full Board, assisted by experienced counsel to the Fund and to the independent Trustees. Fund counsel and the independent Trustees’ counsel are independent of the Managers within the meaning and intent of the Securities and Exchange Commission Rules.

Based on its review of the information it received and its evaluations described above, the Board, including a majority of the independent Trustees, decided to continue the Agreements through August 31, 2019. In arriving at its decision, the Board did not identify any factor or factors as being more important than others, but considered all of the above information, and considered the terms and conditions of the Agreements, including the management fees, in light of all the surrounding circumstances.

40        OPPENHEIMER ULTRA-SHORT DURATION FUND

PORTFOLIO PROXY VOTING POLICIES AND GUIDELINES;

UPDATES TO STATEMENT OF INVESTMENTSUnaudited

The Fund has adopted Portfolio Proxy Voting Policies and Guidelines under which the Fund votes proxies relating to securities (“portfolio proxies”) held by the Fund. A description of the Fund’s Portfolio Proxy Voting Policies and Guidelines is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.CALL OPP (225.5677), (ii) on the Fund’s website at www.oppenheimerfunds.com, and (iii) on the SEC’s website at www.sec.gov. In addition, the Fund is required to file FormN-PX, with its complete proxy voting record for the 12 months ended June 30th, no later than August 31st of each year. The Fund’s voting record is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.CALL OPP (225.5677), and (ii) in the FormN-PX filing on the SEC’s website at www.sec.gov.

The Fund files its complete schedule of portfolio holdings with the SEC for the first quarter and the third quarter of each fiscal year on FormN-Q. The Fund’s FormN-Q filings are available on the SEC’s website at www.sec.gov. Beginning in April 2019, the Fund will no longer file FormN-Qs and will instead disclose its portfolio holdings monthly on FormN-PORT, which will also be available on the SEC’s website at www.sec.gov.

Householding—Delivery of Shareholder Documents

This is to inform you about OppenheimerFunds’ “householding” policy. If more than one member of your household maintains an account in a particular fund, OppenheimerFunds will mail only one copy of the fund’s prospectus (or, if available, the fund’s summary prospectus), annual and semiannual report and privacy policy. The consolidation of these mailings, called householding, benefits your fund through reduced mailing expense, and benefits you by reducing the volume of mail you receive from OppenheimerFunds. Householding does not affect the delivery of your account statements.

Please note that we will continue to household these mailings for as long as you remain an OppenheimerFunds shareholder, unless you request otherwise. If you prefer to receive multiple copies of these materials, please call us at1.800.CALL-OPP(225-5677).You may also notify us in writing or via email. We will begin sending you individual copies of the prospectus (or, if available, the summary prospectus), reports and privacy policy within 30 days of receiving your request to stop householding.

41        OPPENHEIMER ULTRA-SHORT DURATION FUND

OPPENHEIMER ULTRA-SHORT DURATION FUND

Trustees and Officers	Robert J. Malone, Chairman of the Board of Trustees and Trustee
	Andrew J. Donohue, Trustee
	Richard F. Grabish, Trustee
	Beverly L. Hamilton, Trustee
	Victoria J. Herget, Trustee
	Karen L. Stuckey, Trustee
	James D. Vaughn, Trustee
	Arthur P. Steinmetz, Trustee, President and Principal Executive Officer
	Christopher Proctor, Vice President
	Adam S. Wilde, Vice President
	Cynthia Lo Bessette, Secretary and Chief Legal Officer
	Jennifer Foxson, Vice President and Chief Business Officer
	Mary Ann Picciotto, Chief Compliance Officer and Chief Anti-Money
	Laundering Officer
	Brian S. Petersen, Treasurer and Principal Financial & Accounting Officer
Manager	OFI Global Asset Management, Inc.
Sub-Adviser	OppenheimerFunds, Inc.
Distributor	OppenheimerFunds Distributor, Inc.
Transfer and Shareholder	OFI Global Asset Management, Inc.
Servicing Agent
Sub-Transfer Agent	Shareholder Services, Inc.
	DBA OppenheimerFunds Services
Independent Registered	KPMG LLP
Public Accounting Firm
Legal Counsel	Ropes & Gray LLP
	The financial statements included herein have been taken from the records of the Fund without examination of those records by the independent registered public accounting firm.

© 2019 OppenheimerFunds, Inc. All rights reserved.

42        OPPENHEIMER ULTRA-SHORT DURATION FUND

PRIVACY NOTICE

As an Oppenheimer fund shareholder, you are entitled to know how we protect your personal information and how we limit its disclosure.

Information Sources

We obtainnon-public personal information about our shareholders from the following sources:

● Applications or other forms.

● When you create a user ID and password for online account access.

● When you enroll in eDocs Direct,^SMour electronic document delivery service.

● Your transactions with us, our affiliates or others.

● Technologies on our website, including: “cookies” and web beacons, which are used to collect data on the pages you visit and the features you use.

If you visit oppenheimerfunds.com and do not log on to the secure account information areas, we do not obtain any personal information about you. When you do log on to a secure area, we do obtain your user ID and password to identify you. We also use this information to provide you with products and services you have requested, to inform you about products and services that you may be interested in and assist you in other ways.

We do not collect personal information through our website unless you willingly provide it to us, either directly by email or in those areas of the website that request information. In order to update your personal information (including your mailing address, email address and phone number) you must first log on and visit your user profile.

If you have set your browser to warn you before accepting cookies, you will receive the warning message with each cookie. You can refuse cookies by turning them off in your browser. However, doing so may limit your access to certain sections of our website.

We use cookies to help us improve and manage our website. For example, cookies help us recognize new versus repeat visitors to the site, track the pages visited, and enable some special features on the website. This data helps us provide better service for our website visitors.

Protection of Information

We do not disclose anynon-public personal information (such as names on a customer list) about current or former customers to anyone, except as permitted by law.

Disclosure of Information

Copies of confirmations, account statements and other documents reporting activity in your fund accounts are made available to your financial advisor (as designated by you). We may also use details about you and your investments to help us, our financial service affiliates, or firms that jointly market their financial products and services with ours, to better serve your investment needs or suggest educational material that may be of interest to you. If this requires us to provide you with an opportunity to “opt in” or “opt out” of such information sharing with a firm not affiliated with us, you will receive notification on how to do so, before any such sharing takes place.

Right of Refusal

We will not disclose your personal information to unaffiliated third parties (except as permitted by law), unless we first offer you a reasonable opportunity to refuse or “opt out” of such disclosure.

43        OPPENHEIMER ULTRA-SHORT DURATION FUND

PRIVACY NOTICEContinued

Internet Security and Encryption

In general, the email services provided by our website are encrypted and provide a secure and private means of communication with us. To protect your own privacy, confidential and/ or personal information should only be communicated via email when you are advised that you are using a secure website.

As a security measure, we do not include personal or account information innon-secure emails, and we advise you not to send such information to us innon-secure emails. Instead, you may take advantage of the secure features of our website to encrypt your email correspondence. To do this, you will need to use a browser that supports Secure Sockets Layer (SSL) protocol.

● All transactions conducted via our websites, including redemptions, exchanges and purchases, are secured by the highest encryption standards available. SSL is used to establish a secure connection between your PC and OppenheimerFunds’ server. It transmits information in an encrypted and scrambled format.

● Encryption is achieved through an electronic scrambling technology that uses a “key” to code and then decode the data. Encryption acts like the cable converter box you may have on your television set. It scrambles data with a secret code so that no one can make sense of it while it is being transmitted. When the data reaches its destination, the same software unscrambles the data.

● You can exit the secure area by closing your browser or, for added security, you can use the Log Out button before you close your browser.

Other Security Measures

We maintain physical, electronic and procedural safeguards to protect your personal account information. Our employees and agents have access to that information only so that they may offer you products or provide services, for example, when responding to your account questions.

How You Can Help

You can also do your part to keep your account information private and to prevent unauthorized transactions. If you obtain a user ID and password for your account, safeguard that information. Strengthening your online credentials–your online security profile–typically your user name, password, and security questions and answers, can be one of your most important lines of defense on the Internet. For additional information on how you can help prevent identity theft, visit https://www. oppenheimerfunds.com/security.

Who We Are

This joint notice describes the privacy policies of the Oppenheimer funds, OppenheimerFunds, Inc., each of its investment adviser subsidiaries, OppenheimerFunds Distributor, Inc. and OFI Global Trust Co. It applies to all Oppenheimer fund accounts you presently have, or may open in the future, using your Social Security number—whether or not you remain a shareholder of our funds. This notice was last updated as of November 2017. In the event it is updated or changed, we will post an updated notice on our website at oppenheimerfunds.com. If you have any questions about this privacy policy, email us by clicking on theContact Us section of our website at oppenheimerfunds.com, write to us at P.O. Box 5270, Denver, CO 80217-5270, or call us at800 CALL OPP (225 5677).

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47        OPPENHEIMER ULTRA-SHORT DURATION FUND

	Visit us at oppenheimerfunds.com for24-hr access to account information and transactions or call us at 800.CALL OPP (800.225.5677) for24-hr automated information and automated transactions. Representatives also available Mon–Fri8am-8pm ET.
Visit Us oppenheimerfunds.com Call Us 800 225 5677 Follow Us
	Oppenheimer funds are distributed by OppenheimerFunds Distributor, Inc. 225 Liberty Street, New York, NY 10281-1008 © 2019 OppenheimerFunds Distributor, Inc. All rights reserved. RS1740.001.0119 March 25, 2019

Item 2. Code of Ethics.

Not applicable to semiannual reports.

Item 3. Audit Committee Financial Expert.

Not applicable to semiannual reports.

Item 4. Principal Accountant Fees and Services.

Not applicable to semiannual reports.

Item 5. Audit Committee of Listed Registrants

Not applicable.

Item 6. Schedule of Investments.

a) Not applicable. The complete schedule of investments is included in Item 1 of this FormN-CSR.

b) Not applicable.

Item 7. Disclosure of Proxy Voting Policies and Procedures forClosed-End Management Investment Companies.

Not applicable.

Item 8. Portfolio Managers ofClosed-End Management Investment Companies.

Not applicable.

Item 9. Purchases of Equity Securities byClosed-End Management Investment Company and Affiliated Purchasers.

Not applicable.

Item 10. Submission of Matters to a Vote of Security Holders.

The Fund’s Governance Committee Provisions with Respect to Nominations of Directors/Trustees to the Respective Boards

None

Item 11. Controls and Procedures.

Based on their evaluation of the registrant’s disclosure controls and procedures (as defined in rule30a-3(c) under the Investment Company Act of 1940 (17 CFR270.30a-3(c)) as of 1/31/2019, the registrant’s principal executive officer and principal financial officer found the registrant’s disclosure controls and procedures to provide reasonable assurances that information required to be disclosed by the registrant in the reports that it files under the Securities Exchange Act of 1934 (a) is accumulated and communicated to registrant’s management, including its principal executive officer and principal financial officer, to allow timely decisions regarding required disclosure, and (b) is recorded, processed, summarized and reported, within the time

periods specified in the rules and forms adopted by the U.S. Securities and Exchange Commission.

There have been no changes in the registrant’s internal controls over financial reporting that occurred during the registrant’s second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Disclosure of Securities Lending Activities forClosed-End Management Investment Companies.

Not applicable.

Item 13. Exhibits.

(a) (1) Exhibit attached hereto.

(2) Exhibits attached hereto.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Oppenheimer Ultra-Short Duration Fund
By:	/s/ Arthur P. Steinmetz
	Arthur P. Steinmetz
	Principal Executive Officer
Date:	3/15/2019

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By:	/s/ Arthur P. Steinmetz
	Arthur P. Steinmetz
	Principal Executive Officer
Date:	3/15/2019

By:	/s/ Brian S. Petersen
	Brian S. Petersen
	Principal Financial Officer
Date:	3/15/2019