McCargo made her feature film debut in the crime comedy Dead Heat on a Merry-Go-Round in 1966, which was also the debut film of Harrison Ford. Subsequent film roles included: Buona Sera, Mrs. Campbell in 1968 (playing opposite Peter Lawford, Gina Lollobrigida, Shelley Winters, Telly Savalas, and Phil Silvers); The Undefeated in 1969 (with John Wayne and Rock Hudson); and Doctors' Wives in 1971. McCargo also became known for her television role as Harriet Roberts on the nighttime soap, Falcon Crest.