His most famous role was starring as frontier capitalist Sgt. Morgan O'Rourke in F Troop (1965–1967). Though F Troop lasted only two seasons on ABC, the series has been in constant syndication since, reaching three generations of viewers. (Ironically, two of his Gunsmoke episodes feature Tucker in his cavalry uniform again, as the comic "Sergeant Holly," (1970) who in one scene "marries" and spends a hectic night with Miss Kitty.) He appeared in many television series, including ABC's Channing a drama about college life during the 1963-1964 season. In 1961, he appeared on NBC in Audie Murphy's short-lived western series Whispering Smith.
Following F Troop, Tucker returned to films in character parts (Barquero and Chisum, both 1970) and occasional leads (1975's The Wild McCullochs). On television, Tucker was a frequent guest star, including a total of six appearances on Gunsmoke and the recurring role of Jarvis Castleberry, Flo's estranged father on the 1976-1985 TV series, Alice and its spinoff, Flo. Tucker was a regular on three series after F Troop: Dusty's Trail (1973) with Bob Denver; The Ghost Busters (1975–76) which reunited him with F Troop co-star Larry Storch; and Filthy Rich playing the second Big Guy Beck. (1982–83). He continued to be active on stage as well, starring in the national productions of Plaza Suite, Show Boat, and That Championship Season.
Tucker suffered from severe alcoholism in his final years, but returned to the big screen after an absence of several years, in the Cannon Films action film Thunder Run (1986), playing the hero, trucker Charlie Morrison. His final film appearance was Outtakes, a low-budget imitation of The Groove Tube.
His feature film comeback unfortunately was short-lived. He died from lung cancer and emphysema on October 25, 1986, five months after the film's theatrical release. He was interred in Forest Lawn - Hollywood Hills Cemetery in Los Angeles.