Crowton served as LSU's offensive coordinator and quarterback coach for four years, a span that saw the Tigers win a national championship and post a 40-13 overall mark.
"I appreciate all that Gary did for LSU during his four years with us," Miles said. "Gary helped us win a lot of games over the last four years, including a national championship. He's an outstanding coach and a man of great character.
"We wish him and his family well in any of their future endeavors."
Miles said that a search for Crowton's replacement will begin immediately.