X0508 4 2024-03-01 0000354190 Arthur J. Gallagher & Co. AJG 0001589933 GALLAGHER THOMAS JOSEPH 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 VICE PRESIDENT 0 Non-qualified Stock Option 243.54 2024-03-01 4 A 0 15070 0 A 2031-03-01 Common Stock 15070 15070 D Phantom Stock 2024-03-04 4 I 0 2467.82 243.13 A Common Stock 2467.82 15709.821 D One-third of this stock option becomes exercisable on each of the 3rd, 4th, and 5th anniversaries of the grant date. Each share of phantom stock represents a right to receive one share of Gallagher common stock. These shares represent awards under the Age 62 Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the reporting person. Participants vest in these awards when they attain age 62, or after a one-year period for participants who have attained age 61. /s/ Ryan Session, by power of attorney 2024-03-05