He is best known for his role as Detective Stan "Wojo" Wojciehowicz on the sitcom Barney Miller (1975–1982), which earned him two consecutive Primetime Emmy Award for Outstanding Supporting Actor in a Comedy Series nominations.

[2] Gail also won the 2019 and 2021 Daytime Emmy Award for Best Supporting Actor for his role as Mike Corbin on the soap opera General Hospital.

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.

Gail has starred in other TV series, including Whiz Kids (1983) as Llewellan Farley Jr., an investigative reporter who is friends with a group of teenaged computer hackers.

Gail has made many guest appearances on TV shows such as: Walker, Texas Ranger ("Whitewater"); Cannon, Dr. Quinn, Medicine Woman, Due South, The Streets of San Francisco, Paul Sand in Friends and Lovers, Murder, She Wrote, The Drew Carey Show, Hawaii Five-0, Quantum Leap, Psych, Longmire, Gary Unmarried, NCIS, Scorpion, and Mad Men.

Gail runs Full Circle, a production company that has featured documentaries on such subjects as Agent Orange, Native Americans, and nuclear issues.