McLean commanded a brigade in the XXIII Corps during the Atlanta Campaign and again came into conflict with Howard for alleged failures at the Battle of Pickett's Mill. This time, while assaulting Confederate positions on May 27, 1864, McLean's brigade was to be used as a distraction. But, they separated from the brigade on his left, whom they were supposed to stay linked with, and were not able to provide a distraction. Ultimately, Howard's corps took many casualties. He would later write, "General McLean…disregarded the request and moved off at once…leaving Thomas Wood's and General Richard Johnson's divisions isolated. He (McLean) alleged in excuse that his men were entirely without rations."