His film credits have included The Hanging Garden (for which MacNeill won a Genie Award for Best Supporting Actor in 1997), Geraldine's Fortune, Giant Mine, Lives of Girls and Women, The Events Leading Up to My Death, Dog Park and A History of Violence.
On television, he has had roles in Queer as Folk (as Detective Carl Horvath), Katts and Dog (as Sgt. Callahan), Traders (as Frank Larkin) Star Wars Droids (providing the voice of Nilz Yomm), The Eleventh Hour (as Warren Donohue) and PSI Factor: Chronicles of the Paranormal as Ray Donahue.