The actor, who also played Lt. Dan 'Hondo' Harrelson in 1970s Tv action series S.W.A.T., passed away on 18 May (13).
Forrest spent almost six decades on the big and small screen, appearing in Tv classics like The Virginian, Bonanza and Gunsmoke.
Born in Huntsville, Texas, he was the youngest of 13 children.
After serving as a sergeant in the Army during World War Ii, during which he fought at the Battle of the Bulge, Forrest moved to Los Angeles to study at Ucla.
He graduated in 1950 with a bachelor's degree in theatre arts and became a stagehand at the La Jolla Playhouse, where he was discovered by movie legend Gregory Peck, who helped him land a screen test with Mgm.
By 1953, the young actor had started to make a name for himself thanks to his acclaimed role opposite Jane Wyman in So Big.
His early films also included Prisoner of War, opposite Wyman's husband Ronald Reagan, Rogue Cop and It Happened to Jane. He also played Elvis Presley's half-brother in 1960's Flaming Star, and then he became a household name when he teamed up with John Wayne in The Longest Day in 1962.
Forrest will also be remembered for roles in the movies North Dallas Forty, Mommie Dearest, and 1985's Spies Like Us, in which he played a villain opposite Chevy Chase and Dan Akroyd.
His success was international - Forrest also starred in Bbc crime drama The Baron, the first colour series on U.K. Tv.
In his final role in 2003, he played a truck driver in the movie remake of his hit Tv series S.W.A.T.