In 1945, Sills made her professional stage debut with a Gilbert and Sullivan touring company produced by Jacob J. Shubert, playing twelve cities in the US and Canada, in seven different Gilbert and Sullivan operas. In her 1987 autobiography, she credits that tour with helping to develop the comic timing she soon became famous for: "I played the title role in "Patience", and I absolutely loved the character, because Patience is a very funny, flaky girl. ... I played her as a dumb Dora all the way through and really had fun with the role. ... My Patience grew clumsier and clumsier with each performance, and audiences seemed to like her. ... I found that I had a gift for slapstick humor, and it was fun to exercise it onstage." Sills sang in light operas for several more years.