Lewis on daytime's Guiding Light[1] and Doc Baugh in the film version of Cat on a Hot Tin Roof (1958).

[4] His interest in acting led him to change his collegiate focus, and "he ultimately concluded his college career with a speech major".

(1952), Francis Covers the Big Town (1953), The Girl Rush (1955), Invasion of the Body Snatchers (1956), The Strange One (1957), The Brothers Rico (1957), Some Came Running (1958), Cat on a Hot Tin Roof (1958), The Remarkable Mr. Pennypacker (1959), One Foot in Hell (1960), Underworld U.S.A. (1961), The Young Savages (1961), Ada (1961), Toys in the Attic (1963), Cattle King (1963), The Sand Pebbles (1966), In the Heat of the Night (1967), Hour of the Gun (1967), Death of a Gunfighter (1969), Airport (1970), Lucky Luciano (1973), and Funny Lady (1975).

He continued to make dozens of guest appearances in a wide variety of primetime series, including Bonanza, The F.B.I., Route 66, The Defenders, Rawhide, and Twelve O'Clock High.

In 1964, Gates was nominated for a Tony Award in the category Actor, Supporting or Featured (Dramatic), for his work in A Case of Libel.