His film credits as costume designer include Spartacus, Harold and Maude, Bound for Glory, Pete's Dragon (uncredited), Who'll Stop the Rain, Butch and Sundance: The Early Days, The Man with One Red Shoe, and Heart Like a Wheel.

[7] His first Hollywood job was as a personal secretary to Cary Grant,[6] whose ex-wife, actress Dyan Cannon, Theiss cited as having considerable influence on his career.

The "Theiss Titillation Theory"—which claims that "the degree to which a costume is considered sexy is directly proportional to how accident-prone it appears to be"—is named after him.

in which the revealing top portion consists only of two crossing straps of material that connect in one piece to trousers, and—Theiss's personal favorite—the pink gown featured in the episode "Who Mourns for Adonais?

Patrol, as well as for over a dozen motion pictures, including three Academy Award for Best Costume Design nominations for 1976's Bound for Glory, 1979's Butch and Sundance: The Early Days, and 1983's Heart Like a Wheel.