SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

(Amendment No. 2)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2(a)

Contango Oil & Gas Company

(Name of Issuer)

Common Stock, par value $0.04

(Title of Class of Securities)

21075N20

(CUSIP Number)

Michael Peak

200 Pheasant Run Place

Findlay, OH 45840

(419) 306-9794

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

October 1, 2013

(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 Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to be sent.

The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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This Amendment No. 2 to Schedule 13D supplements and amends the Statement on Schedule 13D filed on May 3, 2013, as amended by Amendment No. 1 to Schedule 13D, filed on May 20, 2013. Capitalized terms used without definitions in this Amendment No. 2 shall have the respective meanings ascribed to them in the Schedule 13D, filed on May 3, 2013, as amended by Amendment No. 1 to Schedule 13D, filed on May 20, 2013.

Responses to each item of this Amendment No. 2 to Schedule 13D are incorporated by reference into the response to each other item, as applicable.

Item 1. Security and Issuer

Item 2. Identity and Background

Item 2 is hereby deleted in its entirety and amended as follows:

(a) This Amendment No. 2 to Schedule 13D is filed each of the following persons (collectively, the “Reporting Persons”):

On October 1, 2013, Joseph J. Romano resigned, and Mr. Michael Peak was appointed as, co-executor of the Estate. As a result of his resignation, Mr. Romano ceased to be a beneficial owner of the shares of Common Stock of the Issuer owned of record by the Estate.

(b) The Reporting Persons’ address is c/o Michael Peak, 200 Pheasant Run Place, Findlay, OH 45840.

(c) Mrs. Peak was appointed co-executor of the Estate on May 8, 2013. Mr. Peak was appointed co-executor of the estate on October 1, 2013 upon the resignation of Mr. Romano as co-executor. Mrs. Peak has a phD in biochemistry. Mr. Peak is an investor.

(d) None of the Reporting Persons has, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

(e) None of the Reporting Persons has, during the last five years, been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which he or she was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or a finding of any violation with respect to such laws.

(f) Mr. Peak is a United States citizen. Mrs. Peak is a citizen of the Czech Republic. The Estate is being administered in the State of Texas.

Item 3. Source and Amount of Funds or Other Consideration

Item 3 is hereby amended and supplemented as follows:

The securities that resulted in each Reporting Person becoming a 5% beneficial owner are those that are deemed to have been acquired by each Reporting Person upon the opening of the Estate and the qualification of Mr. Peak and Mrs. Peak as co-executors of the Estate.

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Item 4. Purpose of Transaction

Item 4 is hereby amended and supplemented as follows:

None of the Reporting Persons have any other current plans or proposals which relate to or would result in any of the events described in clauses (a) through (j) of the instructions to Item 4 of Schedule 13D. The Reporting Persons, however, will take such actions with respect to its investments in the Issuer as deemed appropriate in light of existing circumstances from time to time and reserve the right to acquire or dispose of securities of the Issuer, or to formulate other purposes, plans or proposals in the future depending on market conditions or other factors.

Item 5. Interest in Securities of the Issuer

Item 5 is hereby amended and supplemented as follows:

The Estate and Mrs. Peak may be deemed the beneficial owner of 1,516,000 shares of Common Stock of the Issuer, which represents approximately 8.0% of the Issuer’s outstanding shares of Common Stock based on 19,048,522 outstanding shares of Common Stock of the Issuer as of October 17, 2013, as reported in its Definitive Proxy on Schedule 14A filed with the SEC on May 10, 2013. Mr. Peak may be deemed the beneficial owner of 1,521,000 shares of Common Stock of the Issuer, which represents approximately 8.0% of the Issuer’s outstanding shares of Common Stock, consisting of 1,516,000 shares of Common Stock owned of record by the Estate and 5,000 shares owned of record by Mr. Peak.

The Estate has sole voting and investment power with regard to all 1,516,000 shares of Common Stock that it beneficially owns. Mr. Peak and Mrs. Peak may be deemed to have the shared power to direct the voting and disposition of 1,516,000 shares of Common Stock and Mr. Peak may be deemed to have the sole power to direct the voting and disposition of 5,000 shares of Common Stock. Each of Mrs. Peak and the Estate expressly disclaims beneficial ownership of the securities held by Mr. Peak. Pursuant to Rule 13d-4 of the Exchange Act, each of Mr. Peak and Mrs. Peak expressly disclaims beneficial ownership of the securities beneficially owned by the Estate.

There have been no reportable transactions with respect to the Common Stock of the Issuer within the last 60 days by the Reporting Person, except as described in this Amendment No. 2 to Schedule 13D.

No other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares of Common Stock held by the Reporting Persons.

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

Item 7. Material to Be Filed as Exhibits

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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.

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Exhibit 1

AGREEMENT OF JOINT FILING

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned hereby confirm the agreement by and among them to the joint filing on behalf of them of this Amendment No. 2 to Schedule 13D and any and all further amendments thereto, with respect to the above referenced securities and that this Agreement be included as an Exhibit to such filing. This Agreement may be executed in any number of counterparts each of which shall be deemed to be an original and all of which together shall be deemed to constitute one and the same Agreement.

IN WITNESS WHEREOF, the undersigned hereby execute this Agreement as of this 18th day of December 2013.