Frey received critical acclaim in 1968 for his performance as Harold in off-Broadway's The Boys in the Band. He would go on to appear alongside the rest of the original cast in the 1970 film version, directed by william Friedkin.
Frey was nominated for the Academy Award for Best Supporting Actor for his performance as Motel the tailor in Norman Jewison's 1971 film Fiddler on the Roof (he had appeared in the original Broadway musical production as Mendel, the rabbi's son). His other film credits included roles in The Magic Christian (1969), Tell Me That You Love Me, Junie Moon (1970), Where the Buffalo Roam (1980), Up the Academy (1980), and Tattoo (1981).
On The Mary Tyler Moore Show episode entitled "Ted Baxter's Famous Broadcaster's School," aired February 22, 1975, Frey played the role of Lawrence.
Frey died at the age 49 of an AIDS-related illness in New York on August 24, 1988.