Gail was born in Detroit, Michigan, the son of Mary Elizabeth (Scanlon) and Maxwell Trowbridge Gail, a businessman, and he was raised in Grosse Ile, Michigan. He attended Williams College, and was later an instructor for the University Liggett School before becoming an actor. His acting debut came in 1970 for The Little Fox Theatre in San Francisco, California, playing Chief Bromden in the original stage production of One Flew Over the Cuckoo's Nest. In 1973, he reprised this role in his New York stage debut.
He is best known for his television role as Det. Stan "Wojo" Wojoehowicz in the sitcom Barney Miller (1975-1982). Gail's best known feature film role is in D.C. Cab (1983) as Harold, the owner of the D.C. Cab taxi company. He also directed several episodes of Barney Miller as Maxwell Gail.
In 1984, Gail was featured in the monodrama The Babe on Broadway. This stage play was filmed and later featured on PBS.