Katz was best known for his interviews with Alice B. Toklas, the companion of Gertrude Stein, which he conducted over the period from November 1952-February 1953.
In October 2007, Katz gave a public lecture and performance at Carnegie Mellon University based on his time spent with Toklas in her Paris apartment.
Titled "An Evening With Leon Katz," the performance was staged using reproductions of artworks and some original pieces of furniture from Stein and Toklas's apartment.
His plays include The Three Cuckolds, Sonya, Dracula: Sabbat, Son of Arlecchino, GBS in Love, Beds, Pinocchio, Finnegan's Wake, The Marquis de Sade’s Justine, Amerika, The Odyssey, Swellfoot’s Tears, Toy Show, Shekhina: The Bride, Remembrance of Things Past, and The Making of Americans (an opera based on Stein’s novel with music by composer Al Carmines).
Katz was a contributing dramaturg to Tony Kushner's Pulitzer Prize-winning play, Angels in America.