At the Battle of Cross Keys (June 8, 1862), Steuart commanded the 1st Maryland Infantry, which was attacked by, and successfully fought off, a much larger Federal force. However, Steuart was severely injured in the shoulder by grape shot, and had to be carried from the battlefield. A ball from a canister shot had struck him in the shoulder and broken his collarbone, causing a "ghastly wound". The injury did not heal well, and did not begin to improve at all until the ball was removed under surgery in August. It would prevent him from returning to the field for almost an entire year, until May 1863.