Harris has worked on Broadway in both musical and dramatic roles. He played Tobias Ragg in the 2001 concert performances of Sweeney Todd. In 2002, he performed beside Anne Heche in Proof. In 2003, he took the role of the Emcee in Cabaret alongside Deborah Gibson and Tom Bosley. As a result of his critically acclaimed performance in Cabaret, Harris was named the top-drawing headliner in the role of the Emcee by GuestStarCasting.com, topping fellow celebrity stars John Stamos and Alan Cumming. In 2004, he performed a dual role of the Balladeer and Lee Harvey Oswald on Broadway, in the musical revival of Stephen Sondheim's Assassins. He also sang the role of Charles (first played by Anthony Perkins) on the Nonesuch recording of Sondheim's Evening Primrose, and has portrayed Mark Cohen in the touring company of the musical Rent, a role he mockingly reprised on the January 10, 2009, episode of Saturday Night Live, which he hosted.
In 2010, he directed a production of the rock musical Rent at the Hollywood Bowl; he cast his Beastly co-star Vanessa Hudgens as Mimi. In 2011, Harris played the lead role of Bobby in Stephen Sondheim's Company, with the New York Philharmonic in concert opposite Patti LuPone and others. The same year, he directed The Expert at the Card Table at Broad Stage's Edye in Santa Monica, California.
No singing, no dancing: but the funniest EVAH story about turning 40:
Opposite Patti Lupone in the 2011 reprise of Sondheim's Company: