He was assigned to 8th and I Barracks in Washington, D.C., and his primary duty was serving as honor guard at military funerals at Arlington National Cemetery.

[9] His first public appearance on stage was as the barrister in a university production of Terence Rattigan's The Winslow Boy, directed by H. Donovan Rhynsburger.

During rehearsals for that show, he made his first stage appearance—in a student production of Noël Coward's Hands Across the Sea, directed by Jerry V. Tobias.

In 1958, he won an Obie Award for his performances in Children of Darkness[11] (in which he made the first of many appearances opposite his future wife, actress Colleen Dewhurst), for As You Like It (1958), and for playing the title character in William Shakespeare's Richard III (1957–58) (a performance one critic said was the "angriest" Richard III of all time).

[13] Scott's television debut was in a 1958 adaptation of A Tale of Two Cities for the Dupont Show of the Month directed by Robert Mulligan.

Scott's feature film debut was in The Hanging Tree (1959), starring Gary Cooper and Maria Schell.

Later that year he appeared on Broadway in The Andersonville Trial by Saul Levitt directed by Jose Ferrer, winning critical acclaim for his portrayal of the prosecutor.

This was based on the military trial of the commandant of the infamous Civil War prison camp in Andersonville, Georgia.

He guest-starred on episodes of Sunday Showcase, Playhouse 90, Play of the Week (doing "Don Juan in Hell"), Dow Hour of Great Mysteries, and a Hallmark Hall of Fame production of Winterset, originally written for the stage.

[citation needed] Scott was in much demand for guest shots on TV shows, appearing in episodes of Ben Casey and Naked City.

In 1962, Scott appeared as school teacher Arthur Lilly on NBC's The Virginian, in the episode "The Brazen Bell", in which he recites Oscar Wilde's poem "The Ballad of Reading Gaol".

That same year, he appeared in NBC's medical drama The Eleventh Hour, in the episode "I Don't Belong in a White-Painted House".

He appeared opposite Laurence Olivier and Julie Harris in Graham Greene's The Power and the Glory in a 1961 television production[14] and also performed in The Merchant of Venice (1962) off-Broadway.

Scott was a major creative influence on the show, resulting in conflicts with James T. Aubrey, the head of CBS.

Scott's highest-profile early role was in the Stanley Kubrick–directed Dr. Strangelove, or How I Learned to Stop Worrying and Love the Bomb (1964), in which he played General "Buck" Turgidson.

Scott was cast, under the direction of John Huston in Dino de Laurentiis's The Bible: In the Beginning, which was released by 20th Century Fox in 1966.

[17] Also in 1966, Scott appeared as Jud Barker in the NBC western The Road West (also known as This Savage Land), starring Barry Sullivan, Kathryn Hays, Andrew Prine, and Glenn Corbett.

[20] During the early 1970s, Scott appeared in the made-for-television films Jane Eyre (1970) as Mr. Rochester and The Price (1971), a version of the Arthur Miller play.

Scott returned to television with Fear on Trial (1975); and starred in the disaster film The Hindenburg (1975) for director Robert Wise.

Scott had a big Broadway hit with Neil Simon's Plaza Suite (1968), directed by Mike Nichols.

The show was composed of three separate one-act plays all using the same set, with Scott portraying a different lead character in each act; it ran for 1,097 performances.

Scott directed a production of All God's Chillun Got Wings (1975) which starred Van Devere and only had a short run.

Scott starred in a well-received production of Larry Gelbart's Sly Fox (1976; based on Ben Jonson's Volpone), which ran 495 performances.

He later starred as an Ernest Hemingway-based artist in Islands in the Stream (1977) directed by Schaffner and based on Hemingway's posthumously published novel.

Scott starred in The Changeling (1980), with Melvyn Douglas, John Colicos, Jean Marsh, and Van Devere, for which he received the Canadian Genie Award for Best Foreign Film Actor for his performance.

Scott appeared alongside Timothy Hutton and rising stars Sean Penn and Tom Cruise in the coming-of-age film Taps (1981), and was cast as Fagin in the CBS made-for-TV adaptation of Charles Dickens's Oliver Twist (1982).

At the time the sequel was aired, Scott mentioned in a TV Guide interview that he told the academy to donate his Oscar to the Patton Museum, but since the instructions were never put in writing, it was never delivered.

In 1990, he voiced two villainous roles: Smoke in the television special Cartoon All-Stars to the Rescue and Percival McLeach in the Disney film The Rescuers Down Under.

In the latter play, he had to miss many performances due to illness, with his role being taken over by National Actors Theatre artistic director Tony Randall.

[25] One anecdote relates that one of his stage co-stars, Maureen Stapleton, told the director of Neil Simon's Plaza Suite, "I don't know what to do – I'm scared of him."