In his later career, he became famous as Jock Ewing in the CBS primetime soap opera Dallas, a role he continued until he was too ill from multiple myeloma to perform.

Born in Edgerton in Platte County in northwestern Missouri, Davis attended high school in Dearborn, and the Baptist-affiliated William Jewell College in Liberty.

From 1958–1960, Davis starred as Wes Cameron opposite Lang Jeffries in the role of Skip Johnson in the syndicated adventure series Rescue 8.

In the next-to-the-last Laramie episode, entitled "Trapped" (May 14, 1963), he guest-starred with Tommy Sands, Claude Akins, and Mona Freeman.

In the story line, Slim Sherman (John Smith) finds an injured female kidnap victim in the woods (Freeman).

Davis also appeared in an episode of The High Chaparral and in small roles in the 1971 John Wayne vehicles Rio Lobo (1970) and Big Jake (1971).

After years of relatively low-profile roles, Davis was cast as family patriarch Jock Ewing on Dallas, which debuted in 1978.