Filing Details

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 Amendment No. 1 Sonic Corp. ___________________________________________ (Name of Issuer) Common Stock ___________________________________________ (Title of Class and Securities) 835451105 ___________________________________________ (CUSIP Number of Class of Securities) O. Mason Hawkins Chairman of the Board and C.E.O. and Andrew R. McCarroll Vice President & General Counsel Southeastern Asset Management, Inc. 6410 Poplar Avenue, Suite 900 Memphis, TN 38119 (901) 761-2474 ___________________________________________________________ (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) April 3, 2018 ___________________________________________ (Date of Event which Requires Filing of this Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this Schedule because of Sections 240.13d-1(e), 240.13d-1(f), or 240.13d-1(g), check the following box: [X]

CUSIP No. 835451105 13D ___________________________________________________________________ (1) NAMES OF REPORTING PERSONS Southeastern Asset Management, Inc. I.D. No. 62-0951781 ___________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) (b) X ___________________________________________________________________ (3) SEC USE ONLY ___________________________________________________________________ (4) SOURCE OF FUNDS OO: Funds of investment advisory clients ___________________________________________________________________ (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ___________________________________________________________________ (6) CITIZENSHIP OR PLACE OF ORGANIZATION Tennessee ___________________________________________________________________ : (7) SOLE VOTING POWER : (Discretionary Accounts) NUMBER OF SHARES BENEFICIALLY : 0 shares OWNED BY EACH REPORTING PERSON ________________________________ WITH : (8) SHARED OR NO VOTING POWER : 6,370,000 shares (Shared) 66,879 shares (None) ________________________________ : (9) SOLE DISPOSITIVE POWER : (Discretionary Accounts) : 66,879 shares ________________________________ : (10) SHARED DISPOSITIVE POWER : 6,370,000 shares ___________________________________________________________________ (11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,436,879 shares ___________________________________________________________________ (12) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES ___________________________________________________________________ (13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 17.3 % ___________________________________________________________________ (14) TYPE OF REPORTING PERSON IA ___________________________________________________________________ CUSIP No. 835451105 13D ___________________________________________________________________ (1) NAMES OF REPORTING PERSONS Longleaf Partners Small-Cap Fund I.D. No. 62-1376170 ___________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) (b) X ___________________________________________________________________ (3) SEC USE ONLY ___________________________________________________________________ (4) SOURCE OF FUNDS OO: Funds of investment company shareholders ___________________________________________________________________ (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ___________________________________________________________________ (6) CITIZENSHIP OR PLACE OF ORGANIZATION Massachusetts ___________________________________________________________________ : (7) SOLE VOTING POWER : NUMBER OF SHARES BENEFICIALLY : None OWNED BY EACH REPORTING PERSON ________________________________ WITH : (8) SHARED VOTING POWER : 6,370,000 shares ________________________________ : (9) SOLE DISPOSITIVE POWER : : None ________________________________ : (10) SHARED DISPOSITIVE POWER : 6,370,000 shares ___________________________________________________________________ (11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,370,000 shares ___________________________________________________________________ (12) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES ___________________________________________________________________ (13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 17.1 % ___________________________________________________________________ (14) TYPE OF REPORTING PERSON IV ___________________________________________________________________CUSIP No. 835451105 13D ___________________________________________________________________ (1) NAMES OF REPORTING PERSONS O. Mason Hawkins I.D. No. XXX-XX-XXXX ___________________________________________________________________ (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP: (a) (b) X ___________________________________________________________________ (3) SEC USE ONLY ___________________________________________________________________ (4) SOURCE OF FUNDS OO: None ___________________________________________________________________ (5) CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) [ ] ___________________________________________________________________ (6) CITIZENSHIP OR PLACE OF ORGANIZATION Citizen of United States ___________________________________________________________________ : (7) SOLE VOTING POWER : (Discretionary Accounts) NUMBER OF SHARES BENEFICIALLY : None OWNED BY EACH REPORTING PERSON ________________________________ WITH : (8) SHARED VOTING POWER : None ________________________________ : (9) SOLE DISPOSITIVE POWER : None ________________________________ : (10) SHARED DISPOSITIVE POWER : None ___________________________________________________________________ (11) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON None (See Item 2) ___________________________________________________________________ (12) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES ___________________________________________________________________ (13) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 11 0.0% ___________________________________________________________________ (14) TYPE OF REPORTING PERSON IN ___________________________________________________________________ Item 5. Interest In Securities Of The Issuer (a) The aggregate number and percentage of Securities to which this Schedule 13D relates is 6,436,879 shares of the common stock of the Issuer, constituting approximately 17.3% of the 37,154,893 shares outstanding. Common % of outstanding Shares Common Shares Held ___________________________________________________________________ Voting Authority Sole: 0 0.0% Shared: 6,370,000* 17.1% None: 66,879 0.2% Total 6,436,879 17.3% *Consists of shares owned by Longleaf Partners Small-Cap Fund, a series of Longleaf Partners Funds Trust, an open-end management investment company registered under the Investment Company Act of 1940. Dispositive Authority Sole: 66,879 0.2% Shared: 6,370,000* 17.1% Total 6,436,879 17.3% *Consists of shares owned by Longleaf Partners Small-Cap Fund, a series of Longleaf Partners Funds Trust, an open-end management investment company registered under the Investment Company Act of 1940. (b) Southeastern generally has the sole power to dispose of or to direct the disposition of the Securities held for discretionary accounts of its investment clients, and may be granted the sole power to vote or direct the vote of such Securities; such powers may be retained by or shared with the respective clients for shared or non-discretionary accounts. Shares held by any Series of Longleaf Partners Funds Trust are reported in the "shared" category. (c) There have been no purchase or sale transactions in the Securities during the past sixty days. (d) The investment advisory clients of Southeastern have the sole right to receive and, subject to notice, to withdraw the proceeds from the sale of the Securities, and the sole power to direct the receipt of dividends from any of the Securities held for their respective accounts. Such clients may also terminate the investment advisory agreements without penalty upon appropriate notice. Southeastern does not have an economic interest in any of the Securities reported herein. (e) Not applicable. Signatures After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Dated: April 4, 2018 SOUTHEASTERN ASSET MANAGEMENT, INC. By /s/ Andrew R. McCarroll _______________________________ Andrew R. McCarroll General Counsel LONGLEAF PARTNERS SMALL-CAP FUND By: Southeastern Asset Management, Inc. By /s/ Andrew R. McCarroll _______________________________ Andrew R. McCarroll General Counsel O. MASON HAWKINS (Individually) /s/ O. Mason Hawkins _______________________________ Joint Filing Agreement In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, the persons or entities named below agree to the joint filing on behalf of each of them of this Schedule 13G with respect to the Securities of the Issuer and further agree that this joint filing agreement be included as an exhibit to this Schedule 13G. In evidence thereof, the undersigned hereby execute this Agreement as of April 4, 2018. Southeastern Asset Management, Inc. By /s/ Andrew R. McCarroll __________________________________ Andrew R. McCarroll Vice President and General Counsel Longleaf Partners Small-Cap Fund By: Southeastern Asset Management, Inc. By /s/ Andrew R. McCarroll _______________________________ Andrew R. McCarroll Vice President & General Counsel O. Mason Hawkins, Individually /s/ O. Mason Hawkins _______________________________