The Mean Green announced Cosh's hiring Wednesday. He replaces retired John Skladany, who retired after UNT's season.
Cosh was defensive line coach last season at Buffalo, his 12th school in 30 years as a coach. He had stints as defensive coordinator at USF, Kansas State, Maryland, South Carolina, Michigan State, Illinois, Southeast Missouri State and Wisconsin-Oshkosh.
The 55-year-old Cosh has served as an assistant during his career for Bill Snyder, Lou Holtz and Nick Saban.
North Texas coach Dan McCarney says Cosh has a proven record as a coordinator and linebacker coach with a reputation as a tireless recruiter.