On September 14, 1864 he was appointed Colonel of the 57th Massachusetts Infantry returning to the front lines during the Siege of Petersburg. The following day McLaughlen assumed command of the 3rd Brigade, 1st Division, IX Corps. He led it at the Battle of Poplar Springs Church for which he was given a brevet promotion to brigadier general of U.S. Volunteers, and also fought at the Battle of Boydton Plank Road. During the Winter of 1864-1865 McLaughlen was occasionally in command of the 1st Division, IX Corps.