UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q

For the Period Ended JuneSeptember 30, 2015

OR

Commission File Number 000-51274

EQUINOX FRONTIER FUNDS

EQUINOX FRONTIER DIVERSIFIED FUND;

EQUINOX FRONTIER LONG/SHORT COMMODITY FUND;

EQUINOX FRONTIER MASTERS FUND;

EQUINOX FRONTIER BALANCED FUND;

EQUINOX FRONTIER SELECT FUND;

EQUINOX FRONTIER WINTON FUND;

EQUINOX FRONTIER HERITAGE FUND

(Exact Name of Registrant as specified in its Charter)

c/o Equinox Fund Management, LLC

1775 Sherman Street, Suite 2500

Denver, Colorado 80203

(Address of Principal Executive Offices)

(303) 837-0600

(Registrant’s Telephone Number)

Securities to be registered pursuant to Section 12(b) of the Act: None

Securities registered pursuant to Section 12(g) of the Act:

Equinox Frontier Diversified Fund Class 1, Class 2 and Class 3 Units;

Equinox Frontier Long/Short Commodity Fund Class 1, Class 2, Class 3, Class 1a, Class 2a and Class 3a Units;

Equinox Frontier Masters Fund Class 1, Class 2 and Class 3 Units;

Equinox Frontier Balanced Fund Class 1, Class 2, Class 3, Class 1a, Class 2a and Class 3a Units;

Equinox Frontier Select Fund Class 1, Class 2 and Class 3 Units;

Equinox Frontier Winton Fund Class 1, Class 2 and Class 3 Units;

Equinox Frontier Heritage Fund Class 1, Class 2 and Class 3 Units

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files)    Yes  x    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined inRule 1 2b-212b-2 of the Exchange Act).    Yes  ¨    No  x

TABLE OF CONTENTS

Special Note About Forward-Looking Statements

THIS REPORT CONTAINS STATEMENTS WHICH CONSTITUTE FORWARD-LOOKING STATEMENTS WITHIN THE MEANING OF THE PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995 AND OTHER FEDERAL SECURITIES LAWS. THESE FORWARD-LOOKING STATEMENTS REFLECT THE MANAGING OWNER’S CURRENT EXPECTATIONS ABOUT THE FUTURE RESULTS, PERFORMANCE, PROSPECTS AND OPPORTUNITIES OF THE TRUST. THE MANAGING OWNER HAS TRIED TO IDENTIFY THESE FORWARD-LOOKING STATEMENTS BY USING WORDS SUCH AS “MAY,” “WILL,” “EXPECT,” “ANTICIPATE,” “BELIEVE,” “INTEND,” “SHOULD,” “ESTIMATE” OR THE NEGATIVE OF THOSE TERMS OR SIMILAR EXPRESSIONS. THESE FORWARD-LOOKING STATEMENTS ARE BASED ON INFORMATION CURRENTLY AVAILABLE TO THE MANAGING OWNER AND ARE SUBJECT TO A NUMBER OF RISKS, UNCERTAINTIES AND OTHER FACTORS, BOTH KNOWN, SUCH AS THOSE DESCRIBED IN THE “RISK FACTORS” SECTION UNDER ITEM 1A AND ELSEWHERE IN THIS REPORT, AND UNKNOWN, THAT COULD CAUSE THE TRUST’S ACTUAL RESULTS, PERFORMANCE, PROSPECTS OR OPPORTUNITIES TO DIFFER MATERIALLY FROM THOSE EXPRESSED IN, OR IMPLIED BY, THESE FORWARD-LOOKING STATEMENTS.

YOU SHOULD NOT PLACE UNDUE RELIANCE ON ANY FORWARD-LOOKING STATEMENTS. EXCEPT AS EXPRESSLY REQUIRED BY THE FEDERAL SECURITIES LAWS, THE MANAGING OWNER UNDERTAKES NO OBLIGATION TO PUBLICLY UPDATE OR REVISE ANY FORWARD-LOOKING STATEMENTS OR THE RISKS, UNCERTAINTIES OR OTHER FACTORS DESCRIBED HEREIN, AS A RESULT OF NEW INFORMATION, FUTURE EVENTS OR CHANGED CIRCUMSTANCES OR FOR ANY OTHER REASON AFTER THE DATE OF THIS REPORT.

UNLESS EXPRESSLY STATED OTHERWISE, ALL INFORMATION IN THIS REPORT IS AS OF JUNESEPTEMBER 30, 2015, AND THE MANAGING OWNER UNDERTAKES NO OBLIGATION TO UPDATE THIS INFORMATION.

PART I. FINANCIAL INFORMATION

The Series of Equinox Frontier Funds

Statements of Financial Condition

JuneSeptember 30, 2015 (Unaudited) and December 31, 2014

The accompanying notes are an integral part of these financial statements.

The Series of Equinox Frontier Funds

Statements of Financial Condition

September 30, 2015 (Unaudited) and December 31, 2014

The accompanying notes are an integral part of these financial statements.

The Series of Equinox Frontier Funds

Statements of Financial Condition

JuneSeptember 30, 2015 (Unaudited) and December 31, 2014

The accompanying notes are an integral part of these financial statements.

The Series of Equinox Frontier Funds

Statements of Financial Condition

June 30, 2015 (Unaudited) and December 31, 2014

The accompanying notes are an integral part of these financial statements.

The Series of Equinox Frontier Funds

ConsolidatedCondensed Schedule of Investments

September 30, 2015 (Unaudited)

June 30, 2015