Harrison portrayed the title character in the science fiction series ''
Logan's Run (1977–78), after which he played Levi Zendt in the NBC miniseries Centennial'' (1978), based on James Michener's epic novel of the same name, which was first televised on NBC from October 1978 to February 1979. Harrison appeared on an episode of
M*A*S*H before garnering fame in 1979 with the role of surgeon Dr. George "Gonzo" Gates on
Trapper John, M.D., starring opposite
Pernell Roberts. The medical drama was spun off from
M*A*S*H. Harrison remained as Gonzo on
Trapper John until the middle of the show's seventh season, when he decided to leave for other ventures. The series continued for several more episodes without Harrison, but concluded its run at the end of the 1985–86 season. Harrison's later role as
stripper John Phillips in the 1981 TV movie
For Ladies Only made him a favorite with women and gay men in the 1980s. Harrison spoofed that role in the 1986 miniseries
Fresno, where his character appeared shirtless at every opportunity.
Fresno was also a spoof of the prime-time series
Falcon Crest, where Harrison became a regular three years later in the final season (1989–90). As
Falcon Crest ended production in early 1990, the series' parent studio,
Lorimar Television, cast Harrison in its upcoming CBS sitcom
The Family Man, from producers
Thomas L. Miller and
Robert L. Boyett. The series, which premiered that fall, featured Harrison as a single fireman father raising his four children with the help of his father-in-law, played by
Al Molinaro. Despite a few attempts by CBS to help it build an audience,
The Family Man was cancelled after one season. Harrison later joined the cast of NBC's
Sisters for the 1994–95 season, playing Daniel Albright. In 1996, he starred with
Eric Roberts in ''
It's My Party'', a film based on the true story of a man in the end stages of
AIDS who planned a party to say goodbye to friends and family. From 1999 to 2009, Harrison played the male lead role of Oliver Caldwell in each film of the
Au Pair trilogy. In 1999, Harrison starred as Sheriff Jon Loring in the WB Network's short-lived family drama
Safe Harbor and had recurring roles in series such as
One Tree Hill,
Ringer,
Rizzoli & Isles, and
Chesapeake Shores. In 2011, he had a guest-starring role as a doctor on ABC's
Body of Proof, and he has made guest appearances on many other shows such as
Touched by an Angel,
Judging Amy,
Reunion,
Joey,
Law & Order: Special Victims Unit,
Drop Dead Diva and
Hot in Cleveland. In 2020, Harrison joined the cast of
General Hospital, and played the role of Gregory Chase until he left the ABC soap opera in 2024. Since 2021, Harrison has appeared in the recurring role of Phillip Buckley, father of main characters Evan "Buck" Buckley and Maddie Buckley, in
9-1-1. On stage, Harrison played Billy Flynn in the touring and
Broadway productions of
Chicago, and also appeared as Benjamin Stone in the Broadway revival of
Stephen Sondheim's
Follies and starred in the original Broadway production of
Kander & Ebb's musical
Steel Pier. ==Personal life==