From 1969 to 1976, Shearer was a member of The Credibility Gap, a radio comedy group that included David Lander, Richard Beebe and Michael McKean. The group consisted of "a bunch of newsmen" at KRLA 1110, "the number two station" in Los Angeles. They wanted to do more than just straight news, so they hired comedians who were talented vocalists. Shearer heard about it from a friend so he brought over a tape to the station and nervously gave it to the receptionist. He found out he was hired that same day. The group's radio show was canceled in 1970 by KRLA and in 1971 by KPPC-FM, so they started performing in various clubs and concert venues. While at KRLA, Shearer also interviewed Creedence Clearwater Revival for the "Pop Chronicles" music documentary. In 1973, Shearer appeared as Jim Houseafire on "How Time Flys", an album by The Firesign Theatre's David Ossman. The Credibility Gap broke up in 1976 when Lander and McKean left to perform in the sitcom "Laverne & Shirley". Shearer started working with Albert Brooks, producing one of Brooks' albums and co-writing the film "Real Life" (1979). Shearer also started writing for Martin Mull's television series "Fernwood 2 Night". In the mid-1970s, he started working with Rob Reiner on a pilot for ABC. The show, which starred Christopher Guest, Tom Leopold and McKean, was not picked up.