Born Jo Sullivan in Mounds City, Illinois, it was a Manhattan club that helped launch her professional career. She was heard singing in the nightspot and was subsequently chosen to understudy the role of Laurey near the end of the original Broadway run of Oklahoma!. In 1948 she found herself back in the St. James Theatre in the chorus of the ill-fated Sleepy Hollow. That same year, she landed another chorus job in the Mike Todd musical As the Girls Go.
She studied at The Actor’s Studio and, following numerous auditions, landed the leading role of Rosabella in The Most Happy Fella, where she met and eventually married the show's composer-lyricist, Frank Loesser. Before and after The Most Happy Fella, she appeared in the City Center revivals of Carousel, Wonderful Town with Nancy Walker, Die Fleidermaus, and Show Boat, after which she retired to raise a family.
After the death of Frank Loesser in 1969, she returned to performing, appearing at Manhattan venues such as The Ballroom, The Russian Tea Room, and Michael’s Pub.
In 1989 she introduced her daughter, Emily Loesser, to the New York stage, co-starring with her in Together Again for The First Time at the Kaufman Theatre. They subsequently performed numerous times in concerts and theatres, including tours of Together Again and her late husband’s first musical, Where’s Charley?.
Ms. Loesser was instrumental in preserving and furthering her husband’s musical legacy. She appeared in a Broadway revue of his work, Perfectly Frank, in 1980, and she later suggested using a two-piano arrangement of the score for the Goodspeed Opera House’s production of The Most Happy Fella, which led to a move to Broadway in 1992. She served as artistic associate for that revival as well as the fully orchestrated New York City Opera presentation earlier that same year. (It was permanently added to the New York City Opera repertory.)
In 1992, Ms. Loesser was also involved in getting Guys and Dolls revived on Broadway, a production that starred Tony winners Nathan Lane and Faith Prince and won the Tony Award for Best Revival.
Ms. Loesser was also an active member of Board of Directors of The American Theatre Wing and The Actors Fund.
Ms. Loesser is survived by her daughter, Emily Loesser Stephenson, son-in-law Don Stephenson, long-time companion Jaquin Fink, stepchildren John and Susan Loesser, and four grandchildren: Hallie, Fiona, Frank, and Beau. She was predeceased by her daughter Hannah Loesser, who passed away in 2007.