Mark made his professional acting debut portraying Linus in You’re a Good Man, Charlie Brown in the 1968/69 Washington DC. National Company.This cast was chosen to do a command performance at the Lyndon Johnson White House. In November 1971, Baker appeared at the Mercer O’Casey Theatre playing the Boy in Love Me, Love My Children.
Baker appeared on Broadway in 1974 in the title role of Candide, a performance which earned him a Theatre World Award and a nomination for the Tony Award for Best Featured Actor in a Musical.
In 1976, Mark Baker appeared in the romantic adventure film Swashbuckler. The following year, he supplied the voice acting for Raggedy Andy in the animated film Raggedy Ann & Andy: A Musical Adventure. Mark served as assistant director to Ken Russell in the 1977 film Valentino.
Mark appeared as Otto Kringelein in the Broadway international tour of Grand Hotel at venues throughout America, Canada and Japan, and received a Helen Hayes Award for his performance at the Kennedy Center.
Other venues at which Baker has performed include The Public Theater and what was then referred to as the Martin Beck Theatre. More recently he appeared on a studio recording of George Gershwin’s Tip-Toes in 2001.
Mark spent the last two decades of his life devoted to the revitalization of the Embassy Theatre in his hometown of Cumberland, Maryland, overseeing the operations of the Embassy.