[1] McGillin graduated from Dos Pueblos High School and the University of California, Santa Barbara.
[2] He began his career on television, working as a contract player for Universal Studios,[3] and his early film and TV credits include roles in McMillan & Wife (1976), The Six Million Dollar Man (2 episodes, 1976), Emergency!
Often considered a "tall, dark and handsome" leading man,[citation needed] McGillin originated the role of John Jasper in The Mystery of Edwin Drood at the Imperial Theatre; for his performance he was nominated for a 1986 Tony Award for Best Featured Actor in a Musical.
McGillin starred in the award-winning West End 1995 production of Mack & Mabel and sings on the cast album recording.
[5] He received praise as Molina in the Kander and Ebb musical Kiss of the Spider Woman, replacing Brent Carver in 1994.
"[6] Due to their performances and that of leading lady Vanessa Williams, the show received a rare second cast recording.
[7] McGillin originated a leading role in the world premiere of Stephen Sondheim's musical Bounce at the Goodman Theatre, Chicago, and the Kennedy Center in 2003.
He provided the singing voice of Gregory in South Park: Bigger, Longer & Uncut and he has narrated many books on tape and programs/commercials on television (including the PBS series Nature).