Forrest was born on December 23, 1936, in Waxahachie, Texas, the son of Virginia Allee (née McSpadden) and Frederic Fenimore Forrest, a furniture store owner[2][3] whose greenhouses provided plants for sale in retail stores.[4] He served in the United States Army and later attended Texas Christian University, graduating in 1960 with a bachelor's degree in fine arts.[5] In 1993, he was a recipient of TCU's Distinguished Alumni Award.[6]
Forrest was married three times: to his college girlfriend Nancy Whitaker from 1960 to 1963, to actress Marilu Henner from 1980 to 1983, and lastly to model Nina Dean in 1985. He did not have any children.[5][7]
On television, he played Captain Richard Jenko on the first season of the Fox Television series 21 Jump Street, in 1987. Forrest was subsequently replaced by actor Steven Williams, who played Captain Adam Fuller for the remainder of the series. In 1990, he appeared as private investigator Lomax in the BBC miniseries Die Kinder. He played Sgt. McSpadden in the U.S. Civil War-themed movie Andersonville and real-life U.S. Army General Earle Wheeler in 2002's Path to War, the final film of director John Frankenheimer.