After college, Gallagher began working as comic/musician Jim Stafford’s road manager. Stafford and Gallagher traveled to California in 1969, during which time Gallagher decided to perform himself. He began honing his own comedy act while frequenting both The Comedy Store and The Ice House. He was repeatedly denied appearance on The Tonight Show in the 1970s and 1980s, as Johnny Carson disliked prop comedy. However, he was liked by some of the program’s staff, and Gallagher eventually performed several times on the show when guest hosts were filling in for Carson. Gallagher first appeared on The Tonight Show Dec. 5, 1975, when he demonstrated his prop, “The Tonight Show Home Game”, and Carson noted it was his first appearance. Gallagher again appeared on The Tonight Show on May 9, 1979, a show hosted by Carson.

Gallagher was one of the most popular and recognizable American comedians during the 1980s. He did fourteen comedy specials for Showtime which have been re-broadcast numerous times, notably on Comedy Central.

Running for Governor (as an independent) in the 2003 California recall election, Gallagher finished 16th out of 135 candidates with 5,466 votes.