After tryouts in Wilmington, Washington, D.C. and Boston, Rex premiered on Broadway at the Lunt-Fontanne Theatre on April 25, 1976. Edwin Sherin was credited as director, though Harold Prince had been brought in to assist during the show’s rocky out-of-town tryouts. The Broadway production starred British actor Nicol Williamson, with American actress Penny Fuller playing the dual roles of Henry’s wife Anne Boleyn and daughter Elizabeth. The supporting cast included Tom Aldredge, Barbara Andres, Ed Avanko, Valerie Mahaffey, Stephen D. Newman and – in her first Broadway musical – Glenn Close.

Though many critics praised Rodgers’ score, the reviews were almost universally negative. Clive Barnes of The New York Times called the show “one of the most interminable musicals in years,” and Hobe Morrison of Variety characterized the book as “slow and humorless.” The production ran for only 49 performances, closing on June 5, 1976.