When it seemed that he would be relegated to serving as replacements for stars, Grey was cast by Harold Prince in what would become his signature role, the Master of Ceremonies (Emcee) in the landmark 1966 musical "Cabaret". His performance set the mood and tone for the entire piece. Almost all-sung, the Emcee was a diabolical character who seemingly was orchestrating the moral demise of Germany, or, at the very least, understood the events as they were unfolding. He introduced such stunning Kander and Ebb songs as the creepy opening number, "Wilkommen", and "If You Could See Her", ostensibly a love song with an undercurrent of anti-Semitism. (It was sung to a gorilla with the end line "If you could see her through my eyes, she wouldn't look Jewish at all".) Grey won the Tony Award as Featured or Supporting Actor in a Musical.
Based on this success, the actor was chosen to star as George M Cohan in the biographical musical "George M!" in 1968. Based somewhat on Michael Curtiz's seminal "Yankee Doodle Dandy" (1942), "George M!" offered Grey a tour-de-force role, one in which he demonstrated his gifts as actor, dancer and singer. (He reprised the role in a 1970 NBC production). He returned to Broadway in the short-lived musical "Goodtime Charley" (1975), a musical about Joan of Arc in which he was cast as the Dauphin. Grey subsequently tried his hand at dramas, appearing in the all-star ensemble of John Guare's "Marco Polo Sings a Solo" (1977) and replacing Brad Davis as Ned Weeks in Larry Kramer's "The Normal Heart" (1985), both at the New York Shakespeare Festival's Public Theater.
Grey received over the title billing when he reprised the Emcee in the 20th anniversary revival of "Cabaret" in 1987-88. In 1996, he won new fans and renewed acclaim in the Broadway revival of "Chicago", also by Kander and Ebb. Playing the hapless husband of an accused murderess, he nightly stopped the show with his ironic solo about insignificance, "Mister Cellophane".
Grey's feature work has been sporadic. His musical dance performance was the highlight of the behind-the-scenes-at-a-record-company plotted "Calypso Heat Wave" (1957). After over a decade offscreen, Bob Fosse chose him to reprise the Emcee in "Cabaret". Brilliantly reconceived, the film highlighted the character's decadence and Grey delivered an Oscar-winning supporting performance. He next played a mysterious clairvoyant in Frank Perry's "Man on a Swing" (1974), then appeared as the promoter Nate Salsbury in Robert Altman's "Buffalo Bill and the Indians, or Sitting Bull's History Lesson" 1976). He was excellent as the villainous Lowenstein in "The Seven Per-Cent Solution" (also 1976), but additional film roles were not forthcoming. Despite his fine work, Grey was mostly considered a musical comedy performer and some producers felt he was difficult to cast as he was neither a leading man nor enough of a character type. It was nearly a decade before he returned to features, virtually unrecognizable under Asian makeup as the 75-year-old Korean martial arts master in "Remo Williams: The Adventure Begins" (1985). Stephen Soderbergh cast him as the reptilian and mean-spirited office manager in "Kafka" (1991) and Philip Haas' gave him the role of an eccentric millionaire in "The Music of Chance" (1993). Grey was oddly cast as Josef Goebbels in the experimental "The Empty Mirror" (1996) and that same year also appeared in the direct-to-video sci-fi film noir "Venus Rising".
Since the 1960s, Grey has made guest appearances on numerous variety shows, including those hosted by Carol Burnett, Julie Andrews, Tom Jones, and Engelbert Humperdinck, and variety specials. He filmed the busted pilot "Man on a String" (CBS, 1972) and in the last two decades has served as the host of "Christmas at Radio City Music Hall" (HBO, 1986), and played agent Johnny Hyde in "Marilyn and Me" (ABC, 1991), yet another telling of the relationship between the William Morris powerhouse and the former Norma Jean Baker. Grey made his miniseries debut in "Queenie" (ABC, 1987) and garnered an Emmy nomination for his guest role as a Holocaust survivor on the CBS series "Brooklyn Bridge". In 1995, he narrated and played the title role in TNT's "The Wizard of Oz in Concert: Dreams Come True".
Grey, whose daughter Jennifer Grey is an actress, toured on and off throughout the 70s and 80s with "Cabaret" co-star Liza Minnelli.