Until 2005, he worked regularly on and Off-Broadway, in regional theatre, and in over a dozen national and international tours. As an opera singer, Holgate played leading roles in "La Boheme", "Don Giovanni", and the world premiere of "Philip Marshall", among many others. He had an active career as a concert singer, which included performances at Carnegie Hall and a Broadway revue with his first wife, Dorothy Collins (1926–1994). He and Collins were married from 1966-77. He was featured in the first concert devoted to Stephen Sondheim's work.