McMaster downed Calgary 24-26, 25-21, 25-17, 25-22 to meet the Western Mustangs in the late semi on Friday.
Western defeated the Trinity Western Spartans in a stirring five-set upset win in their quarter-final matchup earlier Thursday.
Led by All-Canadian and game MVP Jori Mantha and fellow outside hitter Stephen Maar, the Marauders hit at an impressive clip from the left side, causing no end of problems for the Calgary defence. Mantha picked up 21 big kills on the night while Maar added 17, and the two combined for just seven errors.
"For us it was just being about to find a rhythm with our serving," said Mantha. "We missed a lot of serves early, but we were finally able to pick that up and get a lot of rhythm. Then we were able to make some plays and play defence around the bad pass and high ball out.
McMaster and Western's pairing guarantees an OUA representative in the national championship game Saturday night in the University of Calgary's Jack Simpson Gym as Ontario continues to chase an elusive CIS men's volleyball championship.
Saturday's final will mark just the second time since 1991 that an OUA team will compete for the Tantramar Trophy, which has only been hoisted by a team from the province once: Ottawa, in 1967.
Earlier, the top-seeded University of Alberta Golden Bears lived up to their pre-tournament billing, making quick work of the Universite de Montreal Carabins with a 3-0 win in their quarter-final match.
Alberta will face the defending CIS men's volleyball champion Universite Laval Rouge et Or.
Laval dispatched the Atlantic champion Dalhousie Tigers in straight sets (25-16, 25-18, 25-22) Thursday afternoon to open the 2014 CIS championship.