[2] Bosco attended St. Peter's Preparatory School in Jersey City,[3] and later studied drama at Catholic University of America, where he had notable success in the title role of William Shakespeare's Richard III.
[5] Bosco appeared in revivals of plays by George Bernard Shaw, including Man and Superman, Saint Joan, Mrs. Warren's Profession, Major Barbara, Heartbreak House (opposite Rex Harrison), and You Never Can Tell, winning Tony nominations for the last three.
[5] Following his Tony-winning performance in the farce Lend Me a Tenor in 1990, Bosco appeared on Broadway in An Inspector Calls (1994), The Heiress (1995), Twelfth Night (1998), Copenhagen (2000), and Twelve Angry Men (2004).
He retired from the stage in 2009 after appearing in the City Center Encores production of Finian's Rainbow, although Bosco lent his voice to Douglas Carter Beane's 2010 play Mr. and Mrs.
Bosco narrated Desert Giant: The World of the Saguaro Cactus by Barbara Bash on the PBS series Reading Rainbow in its sixty-second episode on March 27, 1990.