Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  SOUTHEASTERN ASSET MANAGEMENT INC/TN/
 2. Date of Event Requiring Statement (Month/Day/Year)
12/18/2017		 3. Issuer Name and Ticker or Trading Symbol
SONIC CORP [SONC]
(Last)
(First)
(Middle)
6410 POPLAR AVENUE, SUITE 900		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

MEMPHIS, TN 38119		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 6,436,879
I
Voting and/or investment discretion per investment advisory contracts

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
SOUTHEASTERN ASSET MANAGEMENT INC/TN/
6410 POPLAR AVENUE
SUITE 900
MEMPHIS, TN 38119		     X    

Signatures

/s/ Andrew R. McCarroll, General Counsel, Southeastern Asset Management, Inc. 12/19/2017
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
 
Remarks:
Southeastern Asset Management, Inc. ("Southeastern") does not have a pecuniary interest in the securities.  As a result of a conversion from a Schedule 13G to a Schedule 13D, Southeastern may now be deemed a "beneficial owner" of more than 10% of the company's common stock for Section 16 purposes under Rule 16a-1(a)(1) under the Securities Exchange Act of 1934.  As permitted by Rule 16a-1, this Form 3 shall not be deemed an admission that Southeastern is the beneficial owner of more than 10% of the company's common stock for Section 16 purposes.  The number of securities reported in Table I includes 6,370,000 shares held by Longleaf Partners Small Cap Fund.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

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