Ms. Mercer won her Tony for a character who appeared in only two scenes. But Marge MacDougall, the comically soused floozy that hero C.C. Baxter picks up in a bar, proved to be a gem of a cameo role for the tall, blonde and brassy actress, equipped as it was with some of bookwriter Neil Simon's best jokes, and one of Burt Bacharach and Hal David's zippiest numbers, "A Fact Can Be a Beautiful Thing." Clive Barnes, writing in the New York Times, called her "a tiny-voiced hustler with a heart as big as a saloon." Ms. Mercer also won a Theatre World Award and a Drama Desk Award for her work.
Marian Mercer, an Akron, OH, native, made her Broadway debut in the ensemble of Frank Loesser's Greenwillow in 1960, three years after she moved to New York, after working a few seasons in summer stock. She followed that up by taking over the title role in Rick Besoyan's Off-Broadway hit Little Mary Sunshine. Soon after came a turn in New Faces of 1962.
She played the title role in the 1970 comedy A Place for Polly, which lasted all of one performance, and took part in a revival of Noel Coward's Hay Fever, alongside Shirley Booth, John Williams, Sam Waterston and Roberta Maxwell. She returned to musicals with a 1978 Sammy Davis, Jr., revival of Stop the World—I Want to Get Off, and was the original star of John Guare's Bosoms and Neglect in 1979.
On television, Ms. Mercer was a regular on "The Dom DeLuise Show," "The Wacky World of Jonathan Winters," "The Sandy Duncan Show," "The Andy Williams Show" and the long-lived 1980s sitcom "It's a Living." She also had recurring roles on "Mary Hartman, Mary Hartman," its sequel, "Forever Fernwood," "St. Elsewhere," and "Empty Nest." She continued to act on stage in later years, starring in Miss Margarida's Way for the Katselas Theatre Company in Beverly Hills, and in Habeas Corpus at the Matrix theatre in Los Angeles in 1994.
She is survived by Patrick Hogan, her husband of 31 years, and a daughter, Deidre Whitaker.