13D Filing: Leucadia National and Fiesta Restaurant Group Inc. (FRGI)

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

Under the Securities Exchange Act of 1934

Fiesta
Restaurant Group, Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

31660B101

(CUSIP Number)

Roland T. Kelly

11100 Santa Monica Boulevard, 11th Floor

Los Angeles, CA 90025

Tel: (310) 914-1373

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

June 9, 2017

(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 that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g),
check the following box.  ☐

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Item 1. Security and Issuer.

This statement on Schedule 13D relates to the Common Stock, par value $0.01 per share (the Common Stock), of Fiesta Restaurant Group, Inc.,
a Delaware corporation (the Issuer). The principal executive offices of the Issuer are located at 14800 Landmark Boulevard, Suite 500, Dallas, Texas 75254.

Item 2. Identity and Background.

This Schedule 13D
is being filed by Leucadia National Corporation, a New York corporation (Leucadia), on behalf of itself and its controlled subsidiaries (the Reporting Person). Leucadia is a diversified holding company engaged
through its consolidated subsidiaries in a variety of businesses, including investment banking and capital markets, beef processing, manufacturing, oil and gas exploration and production and asset management. Leucadia also owns investments in
business that engage in diversified holdings, real estate, commercial mortgage banking and servicing, telecommunication services in Italy, automobile dealerships and development of a gold and silver mining project.

The address of the principal office of the Reporting Person is 520 Madison Ave., New York, NY 10022.

The names of Leucadias directors and executive officers (the Scheduled Persons) are provided on Schedule I.

During the last five years, neither the Reporting Person nor, to the knowledge of the Reporting Person, any of the Scheduled Persons, has (i) been
convicted in any criminal proceeding (excluding traffic violations or similar misdemeanors) or (ii) been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction such that, as a result of such proceeding,
such person was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activity subject to, federal or state securities laws or finding any violation with respect to such laws.

Item 3. Source and Amount of Funds or Other Consideration.

From March 1, 2017 through June 9, 2017, the Reporting Person purchased an aggregate of 1,356,295 shares of Common Stock. The securities were
acquired by the Reporting Person using cash from working capital in the amount of approximately $28 million.

Item 4. Purpose of Transaction.

The Reporting Person purchased the Common Stock reported herein for investment purposes. The Reporting Person intends to purchase additional shares of
Common Stock from time to time, if, at such time, the terms of such investment are favorable to the Reporting Person and the Reporting Person deems the investment to be prudent.

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Other than described above, the Reporting Person does not have any plans or proposals of the type referred to in
Items 4(a) through (j) of Schedule 13D. The Reporting Person, however, retains the right to change its intent and to pursue any transaction contemplated in Items 4(a) through (j) of Schedule 13D and, to the extent the Reporting
Persons affiliates operate as broker-dealers, they retain the right to pursue a role as a financial advisor, underwriter or placement agent with respect to any such transaction involving the Issuer and its affiliates.

Item 5. Interest in Securities of the Issuer.

Number of shares as to which the Reporting Person has:

Sole power to vote or to direct the vote: 1,356,295

Shared power to vote or to direct the vote: 0

Sole power to dispose or to direct the disposition of: 1,356,295

Shared power to dispose or to direct the disposition of: 0

During the past sixty days, the Reporting Person engaged in the following open market purchases of Common Stock:

Brian P. Friedman, is the President and a director of Leucadia. Mr. Friedman has also been a director of the Issuer since April 2011. Mr. Friedman
beneficially owns an aggregate of 64,938 shares of Common Stock representing 0.2% of the Issuers outstanding shares. Mr. Friedmans beneficial ownership includes 36,270 shares of Common Stock held directly and 28,668 shares of Common
Stock held indirectly through a partnership.

During the past sixty days, Mr. Friedman engaged in the following acquisition of Common Stock:

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Except as set forth in this Item 5, no person other than each respective record owner of the securities
referred to herein is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities.

Item 6. Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer.

Brian P. Friedman, is the President and a director of Leucadia. Mr. Friedman has also been a director of the Issuer since April 2011.

Item 7. Material to be Filed as Exhibits.

SIGNATURE

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.

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SCHEDULE I

DIRECTORS AND EXECUTIVE OFFICERS OF THE REPORTING PERSON

The following information is provided for each of the directors and executive officers of the Reporting Person: