The Stampeders led from wire-to-wire while avenging losses to the Redblacks in 2016 and to the Toronto Argonauts a year ago.
The Redblacks pulled within three points near the end of the second quarter on a 55-yard catch-and-run touchdown by Julian Feoli-Gudino and a two-point conversion to Jean-Christophe Beaulieu, but that was as close as they would get.
Calgary quickly re-established control with Terry Williams' 97-yard punt return touchdown as time expired in the first half.
Bo Levi Mitchell, who was named the Most Outstanding Player of the regular season and the Grey Cup MVP, went 24-for-36 through the air for 253 yards and two touchdowns against a pair of interceptions.
On the other side, Harris finished with 288 passing yards, one touchdown, and three interceptions. The effort came on the heels of his record-setting game in the Eastern Division Final, where he threw six touchdowns against the Hamilton Tiger-Cats.
Redblacks defensive back Jonathan Rose was allowed to play in the Grey Cup after appealing his one-game suspension from last week's game, where he made contact with an official. He recorded an early interception off Mitchell inside his own end zone.
With the win, Calgary claims its first Grey Cup since defeating the Tiger-Cats in 2014.
The Redblacks made their third visit to the Grey Cup since the debut of the franchise in 2014. They lost 26-20 to the Edmonton Eskimos in 2015.
Copyright © 2018 Score Media Ventures Inc. All rights reserved. Certain content reproduced under license.