Oppenheimer Master Inflation Protected Securities Fund N-CSRS Certified semi-annual shareholder report (management investment company)

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT
INVESTMENT COMPANIES

Investment Company Act file number 811-22420

Oppenheimer Master Inflation Protected Securities Fund

(Exact name of registrant as specified in charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of principal executive offices) (Zip code)

Robert G. Zack, Esq.
OppenheimerFunds, Inc.

Two World Financial Center, 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: January 31

Date of reporting period: 07/30/2010

Item 1. Reports to Stockholders.

July 30, 2010 Oppenheimer Master Inflation Semiannual Report Protected Securities Fund, LLC SEMIANNUAL REPORT Listing of Top Holdings Listing of Investments Financial Statements

TOP HOLDINGS AND ALLOCATIONS

Credit Allocation

	NRSRO-Rated			Manager-Rated			Total
Treasury		100.0	%		—	%		100.0	%
Total		100.0	%		—	%		100.0	%

Percentages are as of July 30, 2010, are subject to change and are dollar-weighted based on the market value of the Fund’s securities and derivatives. The Fund’s investment adviser, OppenheimerFunds, Inc. (“OFI”), determines the “Credit Allocation” of the Fund’s securities and derivatives using ratings by “Nationally Recognized Statistical Rating Organizations” (“NRSROs”), such as Standard & Poor’s Corporation (“S&P”). If two or more NRSROs have assigned a rating to a security, the highest rating is used. For securities rated only by an NRSRO other than S&P, OFI converts that rating to the equivalent S&P credit rating. OFI may use its own credit analysis to assign ratings to securities not rated by an NRSRO using rating denominations similar to those of S&P. Securities issued or guaranteed by the U.S. Government or an agency or instrumentality thereof are assigned a credit rating equal to the sovereign credit rating assigned to the U.S. by S&P. A similar process is used for securities issued or guaranteed by a foreign sovereign or supranational entity. Fund assets invested in Oppenheimer Institutional Money Market Fund are assigned the Fund’s S&P rating, which is currently AAA. More information about securities ratings is contained in the Fund’s Statement of Additional Information.

Portfolio Allocation

U.S. Government Obligations 100.0 %

Portfolio holdings and allocations are subject to change. Percentages are as of July 30, 2010, and are based on the total market value of investments.

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NOTES

Shares of Oppenheimer Master Inflation Protected Securities Fund, LLC are issued solely in private placement transactions that do not involve any “public offering” within the meaning of Section 4(2) of the Securities Act of 1933 (the “Securities Act”), as amended. Investments in the Fund may only be made by certain “accredited investors” within the meaning of Regulation D under the Securities Act, including other investment companies. This report does not constitute an offer to sell, or the solicitation of an offer to buy, any “security” within the meaning of the Securities Act.

The Fund’s investment strategy and focus can change over time. The mention of specific fund holdings does not constitute a recommendation by OppenheimerFunds, Inc.

Shares of the Fund first incepted on 6/2/10.

An explanation of the calculation of performance is in the Fund’s Statement of Additional Information.

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FUND EXPENSES

Fund Expenses. As a shareholder of the Fund, you incur ongoing costs, including management 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 for Actual Expenses are based on an investment of $1,000.00 invested at the beginning of the period, June 2, 2010 (commencement of operations) and held for the period ended July 30, 2010.

The Hypothetical Examples for Comparison Purposes are based on an investment of $1,000.00 invested on February 1, 2010 and held for the six months ended July 30, 2010.

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, 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 Period” 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, and an assumed rate of return of 5% per year before expenses, which is not the 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 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 as front-end or contingent deferred sales charges (loads), or a $12.00 fee imposed annually on accounts valued at less than $500.00 (subject to exceptions described in the Statement of Additional Information). 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.

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FUND EXPENSES Continued

	Beginning		Ending		Expenses
	Account		Account		Paid During
	Value		Value		Period Ended
	June 2, 2010		July 30, 2010		July 30, 20101,2
Actual
	$	1,000.00	$	1,015.00	$	0.78
Hypothetical (5% return before expenses)
		1,000.00		1,022.29		2.40

1.	Actual expenses paid are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 59/365 [to reflect the period from June 2, 2010 (commencement of operations) to July 30, 2010].
2.	Hypothetical expenses paid are equal to the Fund’s annualized expense ratio for that class, multiplied by the average account value over the period, multiplied by 180/365 (to reflect the one-half year period).

The expense ratio for the period from June 2, 2010 (commencement of operations) to July 30, 2010 is as follows:

Expense Ratio

     0.48%

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STATEMENT OF INVESTMENTS July 30, 2010 / Unaudited*

	Principal
	Amount			Value
U.S. Government Obligations—81.3%
U.S. Treasury Inflation-Protected Securities:
0.50%, 4/15/151	$	11,200,000		$	11,487,132
0.625%, 4/15/131		9,500,000			10,040,612
1.375%, 1/15/201		11,500,000			11,922,674
2.50%, 1/15/291,2		9,900,000			11,256,620
2.625%, 7/15/171		10,500,000			12,495,468
Total Investments, at Value (Cost $56,573,389)		81.3	%		57,202,506
Other Assets Net of Liabilities		18.7			13,198,606
Net Assets		100.0	%	$	70,401,112

Footnotes to Statement of Investments

*	July 30, 2010 represents the last business day of the Fund’s 2010 semiannual period. See Note 1 of the accompanying Notes.
1.	Denotes an inflation-indexed security: coupon and principal are indexed to a consumer price index.
2.	All or a portion of the security position is held in collateralized accounts to cover initial margin requirements on open futures contracts and written options on futures, if applicable. The aggregate market value of such securities is $123,080. See Note 5 of accompanying Notes.

Valuation Inputs

Various data inputs are 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)	Level 1-unadjusted quoted prices in active markets for identical assets or liabilities (including securities actively traded on a securities exchange)
2)	Level 2-inputs other than unadjusted quoted prices that are observable for the asset (such as unadjusted quoted prices for similar assets and market corroborated inputs such as interest rates, prepayment speeds, credit risks, etc.)
3)	Level 3-significant unobservable inputs (including the Manager’s own judgments about assumptions that market participants would use in pricing the asset).

The table below categorizes amounts that are included in the Fund’s Statement of Assets and Liabilities as of July 30, 2010 based on valuation input level:

			Level 2—		Level 3—
	Level 1—		Other Significant		Significant
	Unadjusted		Observable		Unobservable
	Quoted Prices		Inputs		Inputs		Value
Assets Table
Investments, at Value:
U.S. Government Obligations	$	—	$	57,202,506	$	—	$	57,202,506
Total Investments, at Value		—		57,202,506		—		57,202,506
Other Financial Instruments:
Futures margins		90,406		—		—		90,406
Total Assets	$	90,406	$	57,202,506	$	—	$	57,292,912

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STATEMENT OF INVESTMENTS Unaudited / Continued

				Level 2—		Level 3—
	Level 1—			Other Significant		Significant
	Unadjusted			Observable		Unobservable
	Quoted Prices			Inputs		Inputs		Value
Liabilities Table
Other Financial Instruments:
Futures margins	$	(15,813	)	$	—	$	—	$	(15,813	)
Total Liabilities	$	(15,813	)	$	—	$	—	$	(15,813	)

Currency contracts and forwards, if any, are reported at their unrealized appreciation/depreciation at measurement date, which represents the change in the contract’s value from trade date. Futures, if any, are reported at their variation margin at measurement date, which represents the amount due to/from the Fund at that date. All additional assets and liabilities included in the above table are reported at their market value at measurement date.

See the accompanying Notes for further discussion of the methods used in determining value of the Fund’s investments, and a summary of changes to the valuation methodologies, if any, during the reporting period.

Futures Contracts as of July 30, 2010 are as follows:

								Unrealized
		Number of		Expiration				Appreciation
Contract Description	Buy/Sell	Contracts		Date		Value		(Depreciation)
U.S. Treasury Long Bonds	Buy		47		9/21/10	$	6,049,781	$	220,565
U.S. Treasury Nts., 2 yr.	Buy		20		9/30/10		4,382,500		18,411
U.S. Treasury Nts., 10 yr.	Sell		22		9/21/10		2,723,875		(73,572	)
								$	165,404

See accompanying Notes to Financial Statements.

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STATEMENT OF ASSETS AND LIABILITIES Unaudited

July 30, 20101
Assets
Investments, at value (cost $56,573,389)—see accompanying statement of investments	$	57,202,506
Cash		13,086,074
Receivables and other assets:
Futures margins		90,406
Interest		67,114
Shares of beneficial interest sold		32,820
Other		1,886
Total assets		70,480,806
Liabilities
Payables and other liabilities:
Shares of beneficial interest redeemed		55,386
Futures margins		15,813
Legal, auditing and other professional fees		6,567
Shareholder communications		1,181
Directors’ compensation		218
Other		529
Total liabilities		79,694
Net Assets—applicable to 6,936,835 shares of beneficial interest outstanding	$	70,401,112
Net Asset Value, Redemption Price Per Share and Offering Price Per Share	$	10.15

1. July 30, 2010 represents the last business day of the Fund’s 2010 semiannual period. See Note 1 of the accompanying Notes.

See accompanying Notes to Financial Statements.

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STATEMENT OF OPERATIONS Unaudited

For the Six Months Ended July 30, 20101,2
Investment Income
Interest	$	175,381
Expenses
Management fees		38,394
Legal, auditing and other professional fees		6,567
Shareholder communications		1,181
Custodian fees and expenses		500
Directors’ compensation		437
Other		331
Total expenses		47,410
Net Investment Income		127,971
Realized and Unrealized Gain
Net realized gain on:
Investments		5,525
Closing and expiration of futures contracts		22,626
Net realized gain		28,151
Net change in unrealized appreciation/depreciation on:
Investments		629,117
Futures contracts		165,404
Net change in unrealized appreciation/depreciation		794,521
Net Increase in Net Assets Resulting from Operations	$	950,643

1.	July 30, 2010 represents the last business day of the Fund’s 2010 semiannual period. See Note 1 of the accompanying Notes.
2.	For the period from June 2, 2010 (commencement of operations) to July 30, 2010.

See accompanying Notes to Financial Statements.

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STATEMENT OF CHANGES IN NET ASSETS

	Period Ended
	July 30, 20101,2
	(Unaudited)
Operations
Net investment income	$	127,971
Net realized gain		28,151
Net change in unrealized appreciation/depreciation		794,521
Net increase in net assets resulting from operations		950,643
Beneficial Interest Transactions
Net increase (decrease) in net assets resulting from beneficial interest transactions:
Proceeds from contributions		70,575,435
Payments for withdrawals		(1,224,966	)
		69,350,469
Net Assets
Total increase		70,301,112
Beginning of period		100,000	3
End of period	$	70,401,112

1.	July 30, 2010 represents the last business day of the Fund’s 2010 semiannual period. See Note 1 of the accompanying Notes.
2.	For the period from June 2, 2010 (commencement of operations) to July 30, 2010.
3.	Reflects the value of the Manager’s initial seed money invested on May 21, 2010.

See accompanying Notes to Financial Statements.

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FINANCIAL HIGHLIGHTS

	Period Ended
	July 30, 20101,2
	(Unaudited)
Per Share Operating Data
Net asset value, beginning of period	$	10.00
Income (loss) from investment operations:
Net investment income3		.02
Net realized and unrealized gain		.13
Total from investment operations		.15
Net asset value, end of period	$	10.15
Total Return, at Net Asset Value4		1.50	%
Ratios/Supplemental Data
Net assets, end of period (in thousands)	$	70,401
Average net assets (in thousands)	$	59,567
Ratios to average net assets:5
Net investment income		1.31	%
Total expenses		0.48	%
Portfolio turnover rate		4	%

1.	July 30, 2010 represents the last business day of the Fund’s semiannual period. See Note 1 of the accompanying Notes.
2.	For the period from June 2, 2010 (commencement of operations) to July 30, 2010.
3.	Per share amounts calculated based on the average shares outstanding during the period.
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. 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.

See accompanying Notes to Financial Statements.

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NOTES TO FINANCIAL STATEMENTS Unaudited

1. Significant Accounting Policies

Oppenheimer Master Inflation Protected Securities Fund, LLC (the “Fund”) is organized as a Delaware limited liability company and registered under the Investment Company Act of 1940, as amended, as a diversified, open-end management investment company. The Fund’s investment objective is to seek total return. The Fund’s investment adviser is OppenheimerFunds, Inc. (the “Manager”). The Fund commenced operations on June 2, 2010.

     Shares of the Fund are issued solely in private placement transactions that do not involve any “public offering” within the meaning of Section 4(2) of the Securities Act of 1933, as amended (the “Securities Act”). Investments in the Fund may only be made by “accredited investors” within the meaning of Regulation D under the Securities Act, including other investment companies. The Fund currently offers one class of shares.

     For federal income tax purposes, the Fund qualifies as a partnership, and each investor in the Fund is treated as the owner of its proportionate share of the net assets, income, expenses, and realized and unrealized gains and losses of the Fund. Accordingly, as a “pass-through” entity, the Fund pays no dividends or capital gain distributions.

     The following is a summary of significant accounting policies consistently followed by the Fund.

Semiannual Period. Since July 30, 2010 represents the last day during the Fund’s semiannual period on which the New York Stock Exchange was open for trading, the Fund’s financial statements have been presented through that date to maintain consistency with the Fund’s net asset value calculations used for shareholder transactions.

Securities Valuation. The Fund calculates the net asset value of its shares as of the close of the New York Stock Exchange (the “Exchange”), normally 4:00 P.M. Eastern time, on each day the Exchange is open for trading.

     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. Unadjusted quoted prices in active markets for identical securities are classified as “Level 1,” inputs other than unadjusted quoted prices for an asset that are observable are classified as “Level 2” and significant unobservable inputs, including the Manager’s judgment about the assumptions that a market participant would use in pricing an asset or liability, are classified as “Level 3.” The inputs used for valuing securities are not necessarily an indication of the risks associated with investing in those securities. A table summarizing the Fund’s investments under these levels of classification is included following the Statement of Investments.

     Securities are valued using unadjusted quoted market prices, when available, as supplied primarily by portfolio pricing services approved by the Board of Directors or dealers.

     Securities traded on a registered U.S. securities exchange are valued based on the last sale price of the security reported on the principal exchange on which it is traded, prior to the time when the Fund’s assets are valued. Securities whose principal exchange is NASDAQ^® are valued based on the official closing prices reported by NASDAQ prior to the time when the Fund’s assets are valued. In the absence of a sale, the security is valued

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NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

1. Significant Accounting Policies Continued

at the last sale price on the prior trading day, if it is within the spread of the current day’s closing “bid” and “asked” prices, and if not, at the current day’s closing bid price. A foreign security traded on a foreign exchange is valued based on the last sale price on the principal exchange on which the security is traded, as identified by the portfolio pricing service used by the Manager, prior to the time when the Fund’s assets are valued. In the absence of a sale, the security is valued at the most recent official closing price on the principal exchange on which it is traded.

     Shares of a registered investment company that are not traded on an exchange are valued at that investment company’s net asset value per share.

     U.S. domestic and international debt instruments (including corporate, government, municipal, mortgage-backed, collateralized mortgage obligations and asset-backed securities) and “money market-type” debt instruments with a remaining maturity in excess of sixty days are valued at the mean between the “bid” and “asked” prices utilizing price quotations obtained from independent pricing services or broker-dealers. Such prices are typically determined based upon information obtained from market participants including reported trade data, broker-dealer price quotations and inputs such as benchmark yields and issuer spreads from identical or similar securities.

     “Money market-type” debt instruments with remaining maturities of sixty days or less are valued at cost adjusted by the amortization of discount or premium to maturity (amortized cost), which approximates market value.

     In the absence of a readily available unadjusted quoted market price, including for securities whose values have been materially affected by what the Manager identifies as a significant event occurring before the Fund’s assets are valued but after the close of the securities’ respective exchanges, the Manager, acting through its internal valuation committee, in good faith determines the fair valuation of that asset using consistently applied procedures under the supervision of the Board of Directors (which reviews those fair valuations by the Manager). Those procedures include certain standardized methodologies to fair value securities. Such methodologies include, but are not limited to, pricing securities 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 adjusted for any discounts related to 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.

     There have been no significant changes to the fair valuation methodologies of the Fund during the period.

Inflation-Indexed Debt Securities. Inflation-indexed debt securities are fixed income securities that are structured to seek to provide protection against inflation. The value of the bond’s principal or the interest rate paid on the bond is adjusted to track changes in

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a stated inflation measure. With respect to inflation-indexed bonds whose principal is adjusted with inflation, if the index measuring inflation falls, the principal value of the inflation-indexed bonds will be adjusted downward, and consequently the interest payable on these securities (calculated with respect to smaller principal amounts) will be reduced. If the index measuring inflation rises, both the principal value and the interest payable (calculated with respect to a larger principal amount) will increase. With respect to inflation-indexed bonds whose interest rate is adjusted with inflation, instead of adjusting the bond’s principal amount, the inflation adjustment is reflected in the coupon payment. Because of this inflation adjustment feature, inflation-protected bonds typically have lower yields than conventional fixed-rate bonds with similar maturities.

Concentration Risk. Focusing on one type of investment, inflation-indexed bonds, rather than a broad spectrum of investments, makes the Fund’s share price particularly sensitive to market, economic and other events that may affect this investment type. The Fund’s investment in inflation-indexed bonds may be speculative and subject to greater price volatility than other types of investments.

Federal Taxes. The Fund, as an entity, will not be subject to U.S. federal income tax. The Fund will be treated for U.S. federal income tax purposes as a partnership, and not as an association taxable as a corporation. Therefore, a tax provision is not required. Each shareholder is required for U.S. federal income tax purposes to take into account, in its taxable year with which (or within which a taxable year of the Fund ends), its distributive share of all items of Fund income, gains, losses, and deductions for such taxable year of the Fund. A shareholder must take such items into account even if the Fund does not distribute cash or other property to such shareholder during its taxable year.

     Although the Fund is treated as a partnership for Federal tax purposes, it is intended that the Fund’s assets, income and distributions will be managed in such a way that investment in the Fund would not cause an investor that is a regulated investment company under Subchapter M of the Code (“RIC”) to fail that qualification.

Directors’ Compensation. The Board of Directors has adopted a compensation deferral plan for independent directors that enables directors to elect to defer receipt of all or a portion of the annual compensation they are entitled to receive from the Fund. For purposes of determining the amount owed to the Director 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 Director. The Fund purchases shares of the funds selected for deferral by the Director 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 directors’ 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.

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NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

1. Significant Accounting Policies Continued

Investment Income. Dividend income is recorded on the ex-dividend date or upon ex-dividend notification in the case of certain foreign dividends where the ex-dividend date may have passed. Non-cash dividends included in dividend income, if any, are recorded at the fair market value of the securities received. Interest income 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 1 Month LIBOR Rate plus 2.00%. 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 directors 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.

Other. The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America 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.

2. Shares of Beneficial Interest

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

	Period Ended July 30, 20101,2
	Units			Amount
Contributions		7,048,428		$	70,575,435
Withdrawals		(121,593	)		(1,224,966	)
Net increase		6,926,835		$	69,350,469

1.	For the period from June 2, 2010 (commencement of operations) to July 30, 2010.
2.	The Fund sold 10,000 shares at a value of $100,000 to the Manager upon seeding of the Fund on May 21, 2010.

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3. Purchases and Sales of Securities

The aggregate cost of purchases and proceeds from sales of securities, for the period ended July 30, 2010, were as follows:

	Purchases		Sales
U.S. government and government agency obligations	$	58,800,022	$	2,294,602

4. 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 as shown in the following table:

Fee Schedule
Up to $1 billion	0.40	%
Over $1 billion	0.35

Transfer Agent Fees. OppenheimerFunds Services (“OFS”), a division of the Manager, acts as the transfer and shareholder servicing agent for the Fund. For the period ended July 30, 2010, the Fund paid no fees to OFS for services to the Fund.

Offering and Organizational Costs. The Manager paid all initial offering and organizational costs associated with the registration and seeding of the Fund.

Waivers and Reimbursements of Expenses. OFS has voluntarily agreed to limit transfer and shareholder servicing agent fees to 0.35% of average annual net assets of the Fund.

     Some of these undertakings may be modified or terminated at any time; some may not be modified or terminated until after one year from the date of the current prospectus, as indicated therein.

5. Risk Exposures and the Use of Derivative Instruments

The Fund’s investment objectives not only permit the Fund to purchase investment securities, they also allow the Fund to enter into various types of derivatives contracts, including, but not limited to, futures contracts, forward foreign currency exchange contracts, credit default swaps, interest rate swaps, total return 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. Central to those strategies are features inherent to derivatives that make them more attractive for this purpose than equity and debt securities: they require little or no initial cash investment, they can focus exposure on only certain selected risk factors, and they may not require the ultimate receipt or delivery of the underlying security (or securities) to the contract. This 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.

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NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

5. Risk Exposures and the Use of Derivative Instruments Continued

Market Risk Factors. In accordance with its investment objectives, the Fund may use derivatives to increase or decrease its exposure to one or more of the following 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 to meet interest and principal payments, or both, as they come due. In general, lower-grade, higher-yield bonds are subject to credit risk to a greater extent than lower-yield, higher-quality bonds.

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 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.

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

Risks of Investing in Derivatives. The Fund’s use of derivatives can result in losses due to unanticipated changes in the market risk factors and the overall market. 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.

     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. 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.

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     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. 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. Associated risks can be different for each type of derivative and are discussed by each derivative type in the notes that follow.

Counterparty Credit Risk. Certain derivative positions are subject to counterparty credit risk, which is the risk that the counterparty will not fulfill its obligation to the Fund. The Fund’s derivative counterparties are financial institutions who are subject to market conditions that may weaken their financial position. The Fund intends to enter into financial transactions with counterparties that the Manager believes to be credit-worthy at the time of the transaction. To reduce this risk the Fund has entered into master netting arrangements, established within the Fund’s International Swap and Derivatives Association, Inc. (“ISDA”) master agreements, which allow the Fund to net unrealized appreciation and depreciation for certain positions in swaps, over-the-counter options, swaptions, and forward currency exchange contracts for each individual counterparty.

Credit Related Contingent Features. The Fund has several credit related contingent features that if triggered would allow its derivatives counterparties to close out and demand payment or additional collateral to cover their exposure from the Fund. Credit related contingent features are established between the Fund and its derivatives counterparties to reduce the risk that the Fund will not fulfill its payment obligations to its counterparties. These triggering features include, but are not limited to, a percentage decrease in the Fund’s net assets and or a percentage decrease in the Fund’s Net Asset Value or NAV. The contingent features are established within the Fund’s ISDA master agreements which govern certain positions in swaps, over-the-counter options and swaptions, and forward currency exchange contracts for each individual counterparty.

Valuations of derivative instruments as of July 30, 2010 are as follows:

	Asset Derivatives		Liability Derivatives
Derivatives not	Statement of Assets		Statement of Assets
Accounted for as	and Liabilities		and Liabilities
Hedging Instruments	Location	Value	Location	Value
Interest rate contracts	Futures margins	$90,406*	Futures margins	$15,813*

* 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.

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NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

5. Risk Exposures and the Use of Derivative Instruments Continued

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	Closing and expiration of futures contracts
Interest rate contracts		$22,626

Amount of Change in Unrealized Gain or (Loss) Recognized on Derivatives
Derivatives Not Accounted for as Hedging Instruments	Futures contracts
Interest rate contracts		$165,404

Futures Contracts

A futures contract is a commitment to buy or sell a specific amount of a financial instrument 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 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.

     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. Subsequent payments (variation margin) are made or received by the Fund each day. The variation margin payments are equal to the daily changes in the contract value and are recorded as unrealized gains and losses.

     Futures contracts are reported on a schedule following the Statement of Investments. Securities held in collateralized accounts to cover initial margin requirements on open futures contracts are noted in the Statement of Investments. Cash held by the broker 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 has purchased futures contracts on various bonds and notes to increase exposure to interest rate risk.

     The Fund has sold futures contracts on various bonds and notes to decrease exposure to interest rate risk.

     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.

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6. Pending Litigation

Since 2009, a number of lawsuits have been filed in federal courts against the Manager, Oppenheimer Funds Distributor, Inc. (the “Distributor”), and certain mutual funds (“Defendant Funds”) advised by the Manager and distributed by the Distributor (but not including the Fund). The lawsuits naming the Defendant Funds also name as defendants certain officers, trustees and former trustees of the respective Defendant Funds. The plaintiffs seek class action status on behalf of purchasers of shares of the respective Defendant Fund during a particular time period. The lawsuits raise claims under federal securities laws alleging that, among other things, the disclosure documents of the respective Defendant Fund contained misrepresentations and omissions, that such Defendant Fund’s investment policies were not followed, and that such Defendant Fund and the other defendants violated federal securities laws and regulations. The plaintiffs seek unspecified damages, equitable relief and an award of attorneys’ fees and litigation expenses.

     In 2009, what are claimed to be derivative lawsuits were filed in state court against the Manager and a subsidiary (but not against the Fund), on behalf of the New Mexico Education Plan Trust. These lawsuits allege breach of contract, breach of fiduciary duty, negligence and violation of state securities laws, and seek compensatory damages, equitable relief and an award of attorneys’ fees and litigation expenses.

     The Distributor and another subsidiary of the Manager have been named as defendants in a putative class action filed in federal court in 2010. The plaintiff, a participant in the State of Texas’ college savings plan, asserts claims on behalf of all persons who invested in qualified 529 plans managed by these subsidiaries of the Manager and which held investments in a certain mutual fund managed by the Manager and distributed by the Distributor. Plaintiff alleges causes of action for “improper investments,” “breach of fiduciary duty,” and “punitive damages” arising from that fund’s investments in 2008 and 2009.

     Other lawsuits have been filed since 2008 in various state and federal courts, against the Manager and certain of its affiliates. Those lawsuits were filed by investors who made investments through an affiliate of the Manager, and relate to the alleged investment fraud perpetrated by Bernard Madoff and his firm (“Madoff”). Those suits allege a variety of claims, including breach of fiduciary duty, fraud, negligent misrepresentation, unjust enrichment, and violation of federal and state securities laws and regulations, among others. They seek unspecified damages, equitable relief and an award of attorneys’ fees and litigation expenses. None of the suits have named the Distributor, any of the Oppenheimer mutual funds or any of their independent Trustees or Directors as defendants. None of the Oppenheimer funds invested in any funds or accounts managed by Madoff.

     The Manager believes that the lawsuits described above are without legal merit and is defending against them vigorously. The Defendant Funds’ Boards of Trustees have also engaged counsel to defend the suits brought against those Funds and the present and former Independent Trustees named in those suits. While it is premature to render any opinion as to the outcome in these lawsuits, or whether any costs that the Defendant

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NOTES TO FINANCIAL STATEMENTS Unaudited / Continued

6. Pending Litigation Continued

Funds may bear in defending the suits might not be reimbursed by insurance, the Manager believes that these suits should not impair the ability of the Manager or the Distributor to perform their respective duties to the Fund, and that the outcome of all of the suits together should not have any material effect on the operations of any of the Oppenheimer funds.

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PORTFOLIO PROXY VOTING POLICIES AND PROCEDURES; UPDATES TO STATEMENTS OF INVESTMENTS Unaudited

The Fund has adopted Portfolio Proxy Voting Policies and Procedures 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 Procedures is available (i) without charge, upon request, by calling the Fund toll-free at 1.800.525.7048, (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 Form N-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 1.800.525.7048, and (ii) in the Form N-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 Form N-Q. The Fund’s Form N-Q filings are available on the SEC’s website at www.sec.gov. Those forms may be reviewed and copied at the SEC’s Public Reference Room in Washington, D.C. Information on the operation of the Public Reference Room may be obtained by calling 1-800-SEC-0330.

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 at 1.800.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.

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OPPENHEIMER MASTER INFLATION PROTECTED SECURITIES FUND, LLC

Directors and Officers	William L. Armstrong, Chairman of the Board of Directors and Director
	George C. Bowen, Director
	Edward L. Cameron, Director
	Jon S. Fossel, Director
	Sam Freedman, Director
	Richard F. Grabish, Director
	Beverly L. Hamilton, Director
	Robert J. Malone, Director
	F. William Marshall, Jr., Director
	William F. Glavin, Jr., Director, President and Principal Executive Officer
	Krishna Memani, Vice President and Portfolio Manager
	Thomas W. Keffer, Vice President and Chief Business Officer
	Mark S. Vandehey, Vice President and Chief Compliance Officer
	Brian W. Wixted, Treasurer and Principal Financial & Accounting Officer
	Robert G. Zack, Vice President and Secretary
Manager	OppenheimerFunds, Inc.
Distributor	OppenheimerFunds Distributor, Inc.
Transfer and Shareholder Servicing Agent	OppenheimerFunds Services
Independent Registered Public Accounting Firm	KPMG llp
Counsel	K&L Gates LLP

©2010 OppenheimerFunds, Inc. All rights reserved.

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PRIVACY POLICY 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 obtain nonpublic 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, our electronic document delivery service

• Your transactions with us, our affiliates or others

• A software program on our website, often referred to as a “cookie,” which indicates which parts of our site you’ve visited

• When you set up challenge questions to reset your password online

If you visit www.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 a better service for our website visitors.

Protection of Information

We do not disclose any non-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

We send your financial advisor (as designated by you) copies of confirmations, account statements and other documents reporting activity in your fund accounts. 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 financial services or 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.

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PRIVACY POLICY NOTICE

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 in non-secure emails, and we advise you not to send such information to us in non-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.

We do not guarantee or warrant that any part of our website, including files available for download, are free of viruses or other harmful code. It is your responsibility to take appropriate precautions, such as use of an anti-virus software package, to protect your computer hardware and software.

• All transactions, including redemptions, exchanges and purchases, are secured by SSL and 128-bit encryption. 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 either 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, do not allow it to be used by anyone else. Also, take special precautions when accessing your account on a computer used by others.

Who We Are

This joint notice describes the privacy policies of the Oppenheimer funds, OppenheimerFunds Distributor, Inc., the trustee of OppenheimerFunds Individual Retirement Accounts (IRAs) and the custodian of the OppenheimerFunds 403(b)(7) tax sheltered custodial accounts. 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 January 16, 2004. In the event it is updated or changed, we will post an updated notice on our website at www.oppenheimerfunds.com. If you have any questions about these privacy policies, write to us at P.O. Box 5270, Denver, CO 80217-5270, email us by clicking on the Contact Us section of our website at www.oppenheimerfunds.com or call us at 1.800.525.7048.

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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.

b) Not applicable.

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

Not applicable.

Item 8. Portfolio Managers of Closed-End Management Investment Companies.

Not applicable.

Item 9. Purchases of Equity Securities by Closed-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

1.

The Fund’s Governance Committee (the “Committee”) will evaluate potential Board candidates to assess their qualifications. The Committee shall have the authority, upon approval of the Board, to retain an executive search firm to assist in this effort. The Committee may consider recommendations by business and personal contacts of current Board members and by executive search firms which the Committee may engage from time to time and may also consider shareholder recommendations. The Committee may consider the advice and recommendation of the Funds’ investment manager and its affiliates in making the selection.

2.

The Committee shall screen candidates for Board membership. The Committee has not established specific qualifications that it believes must be met by a trustee nominee. In evaluating trustee nominees, the Committee considers, among other things, an individual’s background, skills, and experience; whether the individual is an “interested person” as defined in the Investment Company Act of 1940; and whether the individual would be

deemed an “audit committee financial expert” within the meaning of applicable SEC rules. The Committee also considers whether the individual’s background, skills, and experience will complement the background, skills, and experience of other nominees and will contribute to the Board. There are no differences in the manner in which the Committee evaluates nominees for trustees based on whether the nominee is recommended by a shareholder.

3.

The Committee may consider nominations from shareholders for the Board at such times as the Committee meets to consider new nominees for the Board. The Committee shall have the sole discretion to determine the candidates to present to the Board and, in such cases where required, to shareholders. Recommendations for trustee nominees should, at a minimum, be accompanied by the following:

•	the name, address, and business, educational, and/or other pertinent background of the person being recommended;
•	a statement concerning whether the person is an “interested person” as defined in the Investment Company Act of 1940;
•	any other information that the Funds would be required to include in a proxy statement concerning the person if he or she was nominated; and
•	the name and address of the person submitting the recommendation and, if that person is a shareholder, the period for which that person held Fund shares.
The recommendation also can include any additional information which the person submitting it believes would assist the Committee in evaluating the recommendation.

4.

Shareholders should note that a person who owns securities issued by Massachusetts Mutual Life Insurance Company (the parent company of the Funds’ investment adviser) would be deemed an “interested person” under the Investment Company Act of 1940. In addition, certain other relationships with Massachusetts Mutual Life Insurance Company or its subsidiaries, with registered broker-dealers, or with the Funds’ outside legal counsel may cause a person to be deemed an “interested person.”

5.

Before the Committee decides to nominate an individual as a trustee, Committee members and other directors customarily interview the individual in person. In addition, the individual customarily is asked to complete a detailed questionnaire which is designed to elicit information which must be disclosed under SEC and stock exchange rules and to determine whether the individual is subject to any statutory disqualification from serving as a trustee of a registered investment company.

Item 11. Controls and Procedures.

Based on their evaluation of the registrant’s disclosure controls and procedures (as defined in rule 30a-3(c) under the Investment Company Act of 1940 (17 CFR 270.30a-3(c)) as of 07/30/2010, 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. Exhibits.

(a)	(1) Exhibit attached hereto.
	(2) Exhibits attached hereto.
	(3) Not applicable.
(b)	Exhibit 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 Master Inflation Protected Securities Fund

By:	/s/ William F. Glavin, Jr.William F. Glavin, Jr.
	Principal Executive Officer

Date: 09/13/2010

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/ William F. Glavin, Jr.William F. Glavin, Jr.
	Principal Executive Officer

Date: 09/13/2010

By:	/s/ Brian W. WixtedBrian W. Wixted
	Principal Financial Officer

Date: 09/13/2010