13D Filing: Osmium Partners Owns Activist Stake in Cra International, Inc. (CRAI)

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

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

RULE 13d-2(a)

(Amendment No.    )*

CRA
International, Inc.

(Name of Issuer)

Common Stock

(Title of
Class of Securities)

12618T105

(CUSIP Number)

Osmium
Partners, LLC

300 Drakes Landing Road, Suite 172

Greenbrae, CA 94904

Attention: John H. Lewis

Telephone: (415) 785-4044

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

January 6, 2016

(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(b) 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 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.)