He is perhaps best known for his roles in the films The Lawless (1950), When Worlds Collide (1951), Julius Caesar (1953), Blackboard Jungle (1955), Spartacus (1960), Cleopatra (1963), The Outer Limits (1964), and the television series Gimme a Break!

He also performed with several regional theater groups, and then joined Orson Welles's Mercury Theatre in 1937; he remained a member of the troupe until he moved to Hollywood in 1945 after his army service.

In this period, he was cast in a range of plays, such as Valley Forge (1934), Ziegfeld Follies of 1936 (1935), The Masque of Kings (1936), Storm Over Patsy (1936), and Caesar (1937, director Orson Welles).

[3][4] His impersonation of Noël Coward was so remarkable [citation needed] that he was hired for the original cast of the Broadway comedy The Man Who Came to Dinner (1939), in which he played Beverley Carlton.

[8]: 1092 On Gunsmoke, in a 1957 episode titled "Bureaucrat", Hoyt played the part of Rex Propter, a government agent sent to Dodge City, Kansas, to determine why the town had such a bad reputation for gun violence.

In 1958 and 1959, he performed in two episodes of Richard Diamond, Private Detective, appearing as Burnison in "The George Dale Case" and as Harding, Sr. in "Murder at the Mansion".

Also in 1959, Hoyt was cast in an episode ("Three Legged Terror") of The Rifleman, playing the character Gus Fremont, the cruel uncle of Johnny Clover (Dennis Hopper).

He returned to The Rifleman in late 1960 as Civil War veteran Captain Josiah Perry, a man deranged by grief over the loss of his son, in the episode "The Martinet".

Hoyt guest-starred on at least three sitcoms: Bringing Up Buddy, Hogan's Heroes, and Petticoat Junction (in the 1966 episode "Hooterville Valley Project", as Mr. Fletcher).

He appeared as KAOS agent Conrad Bunny in "Our Man in Toyland" on Get Smart, as General Beeker in "Hail to the Chief" on Voyage to the Bottom of the Sea, and as Dr. Mendoza in "I Was a Teenage Monster" on The Monkees.

[12] Hoyt was married twice, first to Marian Virginia Burns from 1935 to 1960, with whom he had one child, and later to Dorothy Oltman Haveman from 1961 to 1991, when he died of lung cancer in Santa Cruz, California.