X0306 4 2021-05-15 0000354190 Arthur J. Gallagher & Co. AJG 0001665268 Cavaness Joel D 2850 GOLF ROAD ROLLING MEADOWS IL 60008-4002 1 Vice President Common Stock 2021-05-15 4 J 0 1524.1 0 A 1524.1 I By Spouse Common Stock (restricted) 2021-05-15 4 J 0 2185 0 A 2185 I By Spouse Phantom Stock 2021-05-15 4 J 0 963.2 0 A Common Stock 963.2 963.2 I By Spouse Non-qualified Stock Option 43.71 2021-05-15 4 J 0 2600 43.71 A 2023-03-17 Common Stock 2600 26200 D Non-qualified Stock Option 56.86 2021-05-15 4 J 0 1600 56.86 A 2024-03-16 Common Stock 1600 24900 D Non-qualified Stock Option 70.74 2021-05-15 4 J 0 1150 70.74 A 2025-03-15 Common Stock 1150 19450 D Non-qualified Stock Option 79.59 2021-05-15 4 J 0 1100 79.59 A 2026-03-14 Common Stock 1100 18350 D Non-qualified Stock Option 86.17 2021-05-15 4 J 0 1310 86.17 A 2027-03-12 Common Stock 1310 20470 D Non-qualified Stock Option 127.90 2021-05-15 4 J 0 1210 127.90 A 2028-03-16 Common Stock 1210 20945 D Deemed acquired due to marriage on May 15, 2021. Consists of 600 RSUs granted 3/16/2017; 500 RSUs granted 3/15/2018; 450 RSUs granted 3/14/2019; 440 RSUs granted 3/12/2020; and 195 RSUs granted 3/16/2021. Restricted stock unit award vesting five years after the date of grant. Each share of phantom stock represents a right to receive one share of Gallagher common stock. This award was granted in 2017 and vests on March 31, 2022. These shares represent awards under the Deferred Cash Participation Plan, a nonqualified deferred compensation plan of the Company, which have been deemed invested in Company common stock at the election of the participant. Participants vest in these awards on the fifth anniversary of the date of grant. One-third of this stock option becomes exerciseable on each of the 3rd, 4th, and 5th anniversaries of the grant date. /s/ Seth Diehl, by power of attorney 2021-05-18