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
                              _______________________________