Her earliest theatrical performances include The Importance of Being Earnest with the Touring Players, Bury The Dead at New York's Cherry Lane Theatre, and Machinal.

During the 1950s, Stanley appeared in numerous live TV shows, and gave an acclaimed performance as Clytemnestra in the New York Shakespeare Festival's 1964 production of Electra, opposite Lee Grant, who played the title role.

In 1966, she took over the role of Yente in Broadway's Fiddler On The Roof from Bea Arthur, leaving in 1971 (after more than 2,000 performances) to open in Neil Simon's The Prisoner of Second Avenue, directed by Mike Nichols.

She recreated her role in the film version of The Prisoner of Second Avenue (1975), and was again cast by Nichols for The Fortune (1975), starring Warren Beatty, Jack Nicholson and Stockard Channing.

[7]: 776  She portrayed Elsie Engelhoff on Drexell's Class[7]: 287  provided the voice for Grandma Ethyl Phillips on Dinosaurs[7] and made guest appearances on such television series as Mad About You (which reunited her with her former My Two Dads co-star, Paul Reiser), Malcolm in the Middle, Mr. Belvedere and Cybill.