Schenck's next appearance was at the First Battle of Bull Run, July 21, 1861, where he commanded a brigade in Brig. Gen. Daniel Tyler's division. After the tide of battle turned against the Union force and many units began to flee the battlefield, parts of Schenck's brigade, along with the United States Regulars under Maj. George Sykes, the brigade of three regiments of Germans under Col. Louis Blenker, the brigade of Col. Erasmus Keyes and the 1st and 2nd Rhode Island Infantry Regiments left the field in relatively good order as the remainder of the Union Army retreated in disorder.