Born Dec. 23, 1943 in Los Angeles, CA, Shearer’s performing career began at age seven at the behest of his piano teacher, who was also a talent agent. He made his screen debut with an uncredited turn in one of Abbott and Costello’s weakest pictures, “Abbott and Costello Go To Mars” (1953), and for the next few years, turned up in juvenile roles on film and in television, including David in “The Robe” (1953), a youthful Jack Benny on “The Jack Benny Show” (CBS, 1950-1965) and a prototype for Eddie Haskell in the pilot for “Leave It To Beaver” (ABC/CBS, 1957-1963). As Shearer grew out of adolescence, he left show business and pursued his education – much to his parents’ approval – eventually landing at U.C.L.A., where he majored in political science, and spent his free time writing extensively for the school’s newspaper.

A graduate stint at Harvard followed, as did tenures with the California State Legislature and the Los Angeles school system. Eventually, he landed at KRLA, an L.A. radio station that was putting a spin on news broadcasting airing satirical reportage, in addition to the “straight” news. The writers and performers behind the satire came to be known as The Credibility Gap, and from 1968-1976, Shearer – along with New York actors and comedians David L. Lander, Michael McKean and several other writers and newsmen – produced countless hours of comedy sketches and parodies. The group became popular enough to warrant a tour and four albums between 1968-1975 before disbanding in 1976. Lander and McKean’s departure to co-star in the sitcom “Laverne and Shirley,” (ABC, 1976-1983) was often cited as the main resort for the group’s collapse.

Shearer drifted a bit during the post-Credibility Gap years. He appeared in small roles in several films and television series, including “Serpico” (NBC, 1976-77), and co-wrote the faux documentary/comedy “Real Life” (1979) with Albert Brooks. In 1978, he joined the writing staff of “Fernwood 2Nite” (syndicated, 1976-77), a satirical talk show spin-off from the sitcom, “Mary Hartman, Mary Hartman” (syndicated, 1976-1977), as well as its follow-up series, “America 2-Night” (1978-79). The latter program would earn him an Emmy nomination in 1978. He also starred alongside McKean, Christopher Guest, Rob Reiner, Billy Crystal, Martin Mull and several others in “The T.V. Show” (ABC, 1979), a short-lived sketch comedy series.

Following that show’s demise, Shearer joined the cast and writing staff of “Saturday Night Live” (NBC, 1975- ) during a period when the program was in a state of upheaval over losing its key cast members. Despite a 1980 Emmy nomination, he was not a good fit for the show’s broad sensibilities, and departed in the early eighties when producer/creator Lorne Michaels quit the show. Shearer would return briefly for the 1984-85 season (where he would appear with friends Billy Crystal and Christopher Guest), but left for good shortly thereafter. In 1983, Shearer began broadcasting “Le Show,” a sketch comedy/satire radio show from Santa Monica, CA radio station, KCRW. The program, which was eventually syndicated nationally, made excellent use of Shearer’s sharp political writing and ability to mimic numerous public figures.

In 1984, Shearer joined Guest, McKean, and Reiner for “This is Spinal Tap,” a largely improvised mock documentary about the travails of a hapless British metal band as it embarks on a disastrous tour of America. Shearer played the band’s unflappable bassist, Derek Smalls, playing his own instrument, as well as contributing to the group’s ridiculous songs – which included “Big Bottom” and “Hellhole.” The film was a modest success, but earned a cult following with music fans and performers alike, many of whom recognized their own foibles in the film. The “band” reunited several times since the release of the film, including a 1992 tour behind their second album, Break Like the Wind, and an appearance at Live Earth in 2007, which was accompanied by a new short documentary by Reiner.

Shearer split his time between acting, writing and directing for most of the 1980s. Among his more notable directorial projects were “The History of White People in America” (1985) and its 1986 sequel. Both were mock documentaries on middle class morays starring Martin Mull. In 1989, he was tapped by producer James L. Brooks – a Credibility Gap fan – to provide a number of voices for a new primetime animated series based on short cartoons that aired as part of “The Tracey Ullman Show” (Fox, 1987-1990). The show, titled “The Simpsons,” became a fan obsession and critical hit, landing countless awards during its history, including 23 Emmys, a Peabody Award, and a citation by Time magazine as the best television series of the 20th century.

Shearer, who voiced some of the show’s best-known supporting characters – including town villain Montgomery Burns (“Excellent…”) and his lovelorn major domo, Smithers; the Simpsons’ religious neighbor Ned Flanders (“Okeley-dokeley!”); Reverend Lovejoy; Dr. Hibbert; and the hapless Principal Skinner – was the only cast member to not win an Emmy for his voice work. He would also join the growing criticism of the show’s quality in its later years. In 2007, he voiced all of his regular characters for “The Simpsons Movie,” the long-awaited big-screen version of the program.

Despite the heavy workload of “The Simpsons,” Shearer found time to take supporting roles in several feature films throughout the 1990s and early 2000s, including “My Best Friend’s Wedding” (1997), “Godzilla” (opposite his “Simpsons” co-star Hank Azaria), “Small Soldiers” (as the voice of an alien action figure, with Spinal Tap’s McKean and Guest providing the others), “Dick” (1999, as G. Gordon Liddy), and “A Mighty Wind,” Guest’s playful skewering of the folk music scene. He reunited with Guest’s improv team for “For Your Consideration” (2006), about the effect of Oscar gossip on a no-budget independent film.

In 2003, Shearer made his theatrical directing debut with “Teddy Bear Picnic,” a mockumentary about the goings-on at a lavish retreat for business executives that was inspired by Bohemian Groves, a secret retreat for politicians and world figures in California. The film, which featured many of his regular collaborators (including McKean), saw a limited release and lukewarm reviews.

In addition to his film and radio work, Shearer published three books: 1993’s Man Bites Town, which compiled his essays for Los Angeles Magazine; It’s the Stupidity, Stupid (1999), about the conservative right’s vendetta against the Clinton Administration; and Not Enough Indians (2006), a comic novel about Native American gaming casinos. He also contributed regularly to the web blog, The Huffington Post, and recorded voices for “Not Today, Thank You,” a radio comedy show for BBC Radio 4.