Bostwick was born in San Mateo, California. He is the son of Elizabeth "Betty" (née Defendorf), a housewife, and Henry "Bud" Bostwick, a city planner and actor. His only sibling, Henry "Pete" Bostwick, was killed in a car accident on July 20, 1973. Bostwick attended San Diego\'s United States International University in 1967, majoring in acting, got his start on the Hillbarn Theatre stage now located in Foster City, and worked for a time as a circus performer. He also attended NYU\'s Graduate Acting Program, graduating in 1968.\n', '
In 1970, Bostwick was a member of a pop group called The Klowns, assembled and promoted by Ringling Bros. and Barnum & Bailey Circus, whose members performed wearing stylized clown makeup and costumes. Their sole album, released in 1970, was produced by Jeff Barry, and generated a minor Billboard hit single, "Lady Love".\n', '
Bostwick replaced C.C. Courtney in the musical Salvation. His next stage appearance was in the 1971 rock opera Soon, which closed after three performances. In 1972, Bostwick originated the role of bad boy Danny Zuko in the stage production of Grease, earning a Tony Award nomination for his performance. This was followed by a voice role as Terr in the English-dubbed version of Fantastic Planet in 1973. He later starred with Tim Curry and Susan Sarandon in The Rocky Horror Picture Show (1975) portraying the character of Brad Majors. He also won a Tony Award for his performance in the 1977 musical The Robber Bridegroom. In 1981, Bostwick starred in the TV series adaptation of the 1978 movie Foul Play, with his role modeled after Chevy Chase\'s and co-star Deborah Raffin in Goldie Hawn\'s part. The following year, he starred in Megaforce. Bostwick starred, along with Carl Weintraub, as Rick Armstrong in the short-lived ABC sitcom Dads during the 1986-87 season. From 1996 to 2002, Bostwick portrayed Randall Winston, the mayor of New York City in the sitcom Spin City opposite Michael J. Fox and his successor, Charlie Sheen. In 2006, Bostwick replaced Peter Scolari as Mr. Tyler, the father of Amanda Bynes\' and Jennie Garth\'s lead characters, on What I Like About You.\n', '