Squibb began working in musical theatre at the St. Louis Muny and trained at the Cleveland Play House, and at the HB Studio. While at the Cleveland Play House, she performed in productions of Marseilles, The Play's the Thing, Goodbye, My Fancy, The Heiress, Detective Story, Antigone, Ladies in Retirement and Bloomer Girl. In 1958, she played Dulcie in The Boyfriend Off-Broadway. In 1959, she starred in an Off-Broadway revival of Lend an Ear with Elizabeth Allen. She made her Broadway debut in the original production of Gypsy starring Ethel Mer…