CRA International Inc. (CRAI): Osmium Partners Lowers Its Stake

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. 1)*

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)

April 18, 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 persons 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.)

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CUSIP No. 12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). John H. Lewis
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     AF
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     United States
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     433,629
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     433,629
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     433,629
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     4.9%
14.		Type of Reporting Person (See Instructions)     IN

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CUSIP No.12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Osmium Partners, LLC
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     AF
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     Delaware
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     433,629
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     433,629
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     433,629
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     4.9%
14.		Type of Reporting Person (See Instructions)     IA, OO

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CUSIP No. 12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Osmium Capital, LP
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (4)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     WC
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     Delaware
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     162,561
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     162,561
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     162,561
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     1.8%
14.		Type of Reporting Person (See Instructions)     PN

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CUSIP No. 12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Osmium Capital II, LP
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (4)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     WC
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     Delaware
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     103,366
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     103,366
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     103,366
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     1.2%
14.		Type of Reporting Person (See Instructions)     PN

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CUSIP No. 12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Osmium Spartan, LP
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     WC
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     Delaware
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     66,700
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     66,700
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     66,700
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     0.8%
14.		Type of Reporting Person (See Instructions)     PN

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CUSIP No. 12618T105

1.		Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Osmium Diamond, LP
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  x
3.		SEC Use Only
4.		Source of Funds     WC
5.		Check Box if Disclosure of Legal Proceeding is Required Pursuant to Items 2(d) or 2(e)    ¨
6.		Citizenship or Place of Organization     Delaware
Number of Shares Beneficially owned by Each Reporting Person With:				7.		Sole Voting Power     0
				8.		Shared Voting Power     101,002
				9.		Sole Dispositive Power     0
				10.		Shared Dispositive Power     101,002
11.		Aggregate Amount Beneficially Owned by Each Reporting Person     101,002
12.		Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    ¨
13.		Percent of Class Represented by Amount in Row (9)     1.1%
14.		Type of Reporting Person (See Instructions)     PN

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EXPLANATORY NOTE

The Reporting Persons beneficial ownership has dropped below the 5% Schedule 13D reporting threshold. Therefore, this amendment No. 1 constitutes the
final amendment to the Reporting Persons Schedule 13D and an exit filing for the Reporting Person and terminates the Reporting Persons obligation to further amend the Schedule 13D.

ITEM 3. Source and Amount of Funds or Other Consideration

Item 3 is hereby amended and restated in its entirety as follows:

The source and amount of funds (excluding commissions) used by the Funds in making their purchase of the shares of Common Stock, which includes Common Stock
issuable upon the exercise of Options exercisable within 60 days (Options), owned by each of them in the aggregate was $9,433,930.66 from working capital.

One or more of the Reporting Persons effect purchases of securities through margin accounts which may extend margin credit to the Reporting Persons as and
when required to open or carry positions in the margin accounts, subject to applicable federal margin regulations, stock exchange rules and brokers credit policies. In such instances, the positions held in the margin accounts are pledged as
collateral security for the repayment of debit balances in the accounts.

ITEM 4. Purpose of Transaction

Item 4 is hereby amended and restated in its entirety as follows:

The Reporting Persons have acquired the Issuers Common Stock for investment purposes, and such purchases have been made in the Reporting Persons
ordinary course of business.

In pursuing such investment purposes, the Reporting Persons may further purchase, hold, vote, trade, dispose or otherwise
deal in the Common Stock at times, and in such manner, as they deem advisable to benefit from changes in market prices of such Common Stock, changes in the Issuers operations, business strategy or prospects, or from sale or merger of the
Issuer. To

evaluate such alternatives, the Reporting Persons will routinely monitor the Issuers operations, prospects, business development,
management, competitive and strategic matters, capital structure, and prevailing market conditions, as well as alternative investment opportunities, liquidity requirements of the Reporting Persons and other investment considerations. Consistent with
its investment research methods and evaluation criteria, the Reporting Persons may discuss such matters with management or directors of the Issuer, other shareholders, industry analysts, existing or potential strategic partners or competitors,
investment and financing professionals, sources of credit and other investors. Such factors and discussions may materially affect, and result in, the Reporting Persons modifying their ownership of the Issuers Common Stock, exchanging
information with the Issuer pursuant to appropriate confidentiality or similar agreements, proposing changes in the Issuers operations, governance or capitalization, or in proposing one or more of the other actions described in subsections (a)
through (j) of Item 4 of Schedule 13D.

The Reporting Persons reserve the right to formulate other plans and/or make other proposals, and take such
actions with respect to their investment in the Issuer, including any or all of the actions set forth in paragraphs (a) through (j) of Item 4 of Schedule 13D, or acquire additional shares or dispose of all the shares beneficially owned by them, in
the public market or privately negotiated transactions. The Reporting Persons may at any time reconsider and change their plans or proposals relating to the foregoing.

ITEM 5. Interest in Securities of the Issuer

Item 5
is hereby amended and restated in its entirety as follows:

(a) The Reporting Persons beneficially own:

(i)

Fund I directly owns 162,561 shares of Common Stock representing 1.8% of all of the outstanding shares of Common Stock of the Issuer.

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(ii)

Fund II directly owns 103,366 shares of Common Stock representing 1.2% of all of the outstanding shares of Common Stock of the Issuer.

(iii)

Fund III directly owns 66,700 shares of Common Stock representing 0.8% of all of the outstanding shares of Common Stock of the Issuer.

(iv)

Fund IV directly owns 101,002 shares of Common Stock representing 1.1% of all of the outstanding shares of Common Stock of the Issuer.

(v)

Osmium Partners, as the general partner of each of the Funds, may be deemed to beneficially own the 433,629 shares of Common Stock held by them, representing 4.9% of all of the outstanding shares of Common Stock of the Issuer.

(vi)

Mr. Lewis individually does not own any shares of Common Stock or Options. However, Mr. Lewis may be deemed to be the beneficial owner of the shares of Common Stock and Options beneficially owned by Osmium Partners.

(vii)

Collectively, the Reporting Persons beneficially own 433,629 shares of Common Stock, representing 4.9% of all of the outstanding shares of Common Stock.

Each Reporting Person disclaims beneficial ownership with respect to any shares of Common Stock other than the shares owned directly and of record by such
Reporting Person.

The percentages set forth in this response are based on the 8,927,972 shares of Common Stock outstanding as of February 26, 2016, as
reported by the Issuer in its Annual Report on Form 10-K for the fiscal year ended January 2, 2016 as filed with the SEC on March 4, 2016.

(b) Osmium
Partners and Mr. Lewis may be deemed to share with Fund I, Fund II, Fund III and Fund IV (and not with any third party) the power to vote or direct the vote of and to dispose or direct the disposition of the 162,561 shares of Common Stock, 103,366
shares of Common Stock, 66,700 shares of Common Stock and 101,002 shares of Common Stock reported herein, respectively.

(c) The following Reporting
Persons engaged in the following open-market transactions with respect to the Issuers Common Stock during the last 60 days:

Osmium Capital,
LP

Transaction Date		Number of Shares				Price per Share				Type of Transaction
2/19/2016			22				0			Option Expiration
2/19/2016			10				0			Option Expiration
3/11/2016			3000				19.9			Sale
3/16/2016			4000				20.04			Sale
3/16/2016			1500				20.04			Sale
3/18/2016			500				20.629			Sale
3/18/2016			4500				20.629			Sale
3/22/2016			2500				20.7172			Sale
3/23/2016			1500				20.264			Sale
3/23/2016			2000				20.264			Sale
3/23/2016			4000				20.264			Sale
3/24/2016			2000				19.6726			Sale
3/30/2016			700				19.9044			Sale
3/30/2016			2396				19.9044			Sale
3/30/2016			3000				19.9044			Sale
3/30/2016			254				19.9044			Sale
3/30/2016			3900				19.9044			Sale
3/30/2016			12750				19.9044			Sale
4/13/2016			1600				19.9575			Sale
4/18/2016			8854				19.8423			Sale
4/18/2016			7000				19.8423			Sale
4/18/2016			1000				19.8423			Sale

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4/18/2016			2000				19.8423			Sale
4/18/2016			2000				19.8423			Sale
4/18/2016			1146				19.8423			Sale
4/18/2016			2000				19.8423			Sale
4/18/2016			1500				19.8423			Sale
4/18/2016			3200				19.8423			Sale
4/18/2016			1300				19.8423			Sale

Osmium Capital II, LP

Transaction Date		Number of Shares				Price per Share				Type of Transaction
2/19/2016			5				0			Option Expiration
2/19/2016			15				0			Option Expiration
3/11/2016			584				19.9			Sale
3/11/2016			1416				19.9			Sale
3/16/2016			2500				20.04			Sale
3/18/2016			1000				20.629			Sale
3/18/2016			3516				20.629			Sale
3/18/2016			400				20.629			Sale
3/18/2016			84				20.629			Sale
3/23/2016			2500				20.264			Sale
3/24/2016			2906				19.6726			Sale
3/24/2016			984				19.6726			Sale
3/24/2016			210				19.6726			Sale
3/30/2016			1700				19.9044			Sale
3/30/2016			6344				19.9044			Sale
3/30/2016			356				19.9044			Sale
3/31/2016			1456				19.8618			Sale
3/31/2016			2100				19.8618			Sale
3/31/2016			144				19.8618			Sale
4/6/2016			2000				19.015			Sale
4/6/2016			544				19.015			Sale
4/6/2016			1000				19.015			Sale
4/6/2016			1456				19.015			Sale
4/18/2016			1000				19.928			Purchase

Osmium Spartan, LP

Transaction Date		Number of Shares				Price per Share				Type of Transaction
2/19/2016			15				0			Option Expiration

Osmium Diamond, LP

Transaction Date		Number of Shares				Price per Share				Type of Transaction
2/19/2016			10				0			Option Expiration
2/22/2016			5000				19.3			Purchase
2/25/2016			1000				19.418			Purchase
4/11/2016			1500				19.545			Sale
4/11/2016			3500				19.545			Sale

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Other than the foregoing, no transactions in the Common Stock have been effected by the Reporting Persons in the
last sixty (60) days.

(d) Not applicable.

(e) Not
applicable.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, the undersigned certify that the information set forth in this statement
is true, complete and correct.

Dated: April 20, 2016

John H. Lewis
Osmium Partners, LLC
Osmium Capital, LP
Osmium Capital II, LP
Osmium Spartan, LP
Osmium Diamond, LP
By:		/s/ John H. Lewis
John H. Lewis, for himself and as Managing Member of Osmium Partners, LLC, for itself and as General Partner of Osmium Capital, LP, Osmium Capital II, LP, Osmium Spartan, LP and Osmium Diamond, LP