X0508 4 2024-11-05 0000354190 Arthur J. Gallagher & Co. AJG 0001185998 CARY RICHARD C 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 Controller, CAO 0 Common Stock 2024-11-05 4 M 0 74087.263 0 A 112526.013 D Common Stock 2024-11-05 4 F 0 32752.264 281.93 D 79773.749 D Common Stock 367.582 I Gallagher 401(k) plan account Phantom Stock 2024-11-05 4 M 0 74087.263 0 D Common Stock 74087.263 619.705 D 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. This filing reports: (1) the distribution, following administrative processing after vesting, of Gallagher common stock in the Age 62 Plan; and (2) the withholding of shares to cover applicable taxes. /s/ Ryan Session, by power of attorney 2024-11-07