The rugged, dark-haired Breck played the gambler and gunfighter Doc Holliday on the ABC/Warner Bros. Television series Maverick as well as Victoria Barkley's (Barbara Stanwyck) hot-tempered middle son Nick in the 1960s ABC/Four Star Western The Big Valley.

He grew up living with his grandparents in Haverhill, Massachusetts, because they felt they could provide a more stable home environment than his father, who often traveled as a jazz musician.

"[3] After post-World War II United States Navy service in the 1940s on the aircraft carrier USS Franklin D. Roosevelt (CV-42), Breck played professional basketball for the Rochester Royals during the 1948–49 season.

He then worked as a ranch hand while studying drama at the University of Houston, and went on to make his on-screen debut in a 1958 film that was eventually released under the title The Beatniks.

That same year, Breck played the role of a bad guy in an episode of Wagon Train, "The Story of Tobias Jones", opposite Lou Costello.

From January 1959 to May 1960, Breck starred as Clay Culhane, the gunfighter-turned-lawyer in the ABC Western Black Saddle, with secondary roles for Russell Johnson, Anna-Lisa, J. Pat O'Malley, and Walter Burke.

Breck was later a contract star with Warner Bros. Television, where he appeared as Doc Holliday on Maverick,[6] a part that had been played twice earlier in the series by Gerald Mohr and by Adam West on ABC's Lawman.

Breck appeared in several other ABC/WB series of the time, such as Cheyenne, 77 Sunset Strip, The Roaring Twenties (as trumpet player Joe Peabody in the episode "Big Town Blues"), and The Gallant Men.

Always spoiling for a fight and frequently wearing leather gloves, Breck's character took the slightest offense to the Barkley name personally and quickly made his displeasure known, as often with his fists as with his vociferous shouts.

Often, this proved to be a mistake, and only through the calming influence of his mother and cooler-headed siblings, Jarrod (Richard Long), half-brother Heath (Lee Majors), sister Audra (Linda Evans), and Eugene (Charles Briles; written out after season one when he was drafted into the Army), would a difficult situation be rectified.

Having been a Barbara Stanwyck admirer since the 1940s, when he was a teenager, Breck developed an on- and off-screen chemistry with her, practicing longer lines and even being a ranch foreman on the set.

[1] In June 2010, Breck's wife Diane announced on his website that he had been suffering from dementia and could no longer sign autographs for fans, although she said that he still read and enjoyed their letters.