Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statements (Form S-8, No. 333-87320 and Form S-8, No. 333-106535) pertaining to the Arthur J. Gallagher & Co. 1988 Nonqualified and Non-Employee Directors’ Stock Option Plans, in the Registration Statement (Form S-8, No. 333-106534) pertaining to the Arthur J. Gallagher & Co. Employee Stock Purchase Plan, in the Registration Statement (Form S-8, No. 333-106539) pertaining to the Arthur J. Gallagher & Co. Restricted Stock Plan, in the Registration Statement (Form S-8, No. 333-159150) pertaining to the Arthur J. Gallagher & Co. 2009 Long-Term Incentive Plan, in the Registration Statement (Form S-8, No. 333-174497) pertaining to the Arthur J. Gallagher & Co. 2011 Long-Term Incentive Plan, in the Registration Statements (Form S-4, No. 333-152710 and Form S-3, No. 333-166533), and in the related Prospectuses, of our reports dated February 14, 2012, with respect to the consolidated financial statements and schedule of Gallagher and the effectiveness of internal control over financial reporting of Gallagher included in this Annual Report (Form 10-K) for the year ended December 31, 2011.

/s/ Ernst & Young LLP

Ernst & Young LLP

Chicago, Illinois

February 14, 2012