[2] He graduated from Douglas MacArthur High School in the northeastern part of San Antonio and from The University of Texas at Austin with a degree in drama.

He portrayed CIA Director George Tenet in Oliver Stone's film W. and, most recently, in 2012, Secretary of War Edwin M. Stanton in Steven Spielberg's Lincoln.

He also appeared multiple times as a regular guest star in MacGyver as the title character's comical best friend, soldier of fortune/bush pilot Jack Dalton.

In 1994 he made a guest appearance along with Jay Leno in the Emmy nominated TV series, Home Improvement.

In 2009, McGill appeared on Law & Order: Special Victims Unit as Gordon Garrison, a zealously bigoted anti-immigration talk-show host who, after sparking a mini-riot in court, sets up the acquittal of the killer.

[6] McGill also played Major Ed Ryan in the third season Babylon 5 episode "Severed Dreams" (which won the 1997 Hugo Award for Best Dramatic Presentation).

McGill portrayed the character of veteran Boston Police Homicide Detective Vince Korsak on the TNT television crime drama, Rizzoli & Isles.

[8] It was reported in February 2017 that he would guest star as a decorated Vietnam War veteran in the television series NCIS.