[3] He began his acting career in 1975 with a summer stock company formed with fellow Guelph students that played Muskoka resorts.
[1] He unsuccessfully auditioned for the festival in 1975, but was hired years later by artistic director Robin Phillips, making his debut in Romeo and Juliet in 1977.
[5] Highlights of his career included his 2004 performance in Timon of Athens,[8] as well as roles in To Kill a Mockingbird, The Seagull, Who's Afraid of Virginia Woolf?.
[5][9] Toronto critic Richard Ouzounian later noted that "Of all the fine actors I've ever seen in the part, only Donaldson gave us the charm as well as the pathos, the hope as well as the despair".
[1][3] He also worked at the Shaw Festival, and in London as part of Robin Phillips' repertory company at the Grand Theatre.
[10] In the late 1990s, he also co-starred in the Atom Egoyan film The Sweet Hereafter[1] and played John Adams in the six-part 1997 PBS television documentary Liberty!