Cornish plowed nine yards past defenders for a touchdown with 1:25 remaining to ensure the Stampeders (13-2) clinched first place in the CFL West Division with a 33-23 victory over the Winnipeg Blue Bombers.
The nine-play winning drive covered 60 yards, with Cornish accounting for 39 of those to record his fifth rushing TD of the season.
"I just follow the blocks," Cornish said. "Our offensive line, they stepped up… When it gets down to the final minutes of the fourth quarter, as we've seen many times this year, they come out, they play their game.
"It makes me look good. I'm just a reflection of their performance."
Cornish, who's missed seven games this season, went into the match with 817 rushing yards — 32 behind league-leader Anthony Allen from Saskatchewan, who plays Sunday.
Winnipeg (6-10) lost its seventh game in a row in front of a season-low crowd of 22,320 at Investors Group Field on a cold, windy night.
The loss didn't officially eliminate the Bombers from playoff contention, but their hopes are slim as they host the B.C. Lions (8-7) next week in a game between clubs trying to get a cross-over berth into the East Division playoff picture.
The defeat was also costly on Winnipeg's quarterback front.
Bombers quarterback Brian Brohm, making his first CFL start in place of injured Drew Willy (hand), was 14-of-23 for 194 yards with no TDs and no picks.
Brohm was injured late in the third quarter and replaced by Robert Marve.
Head coach Mike O'Shea said after the game it's suspected Brohm broke the thumb on his throwing hand. He added it's expected Willy will be ready to play next week.
Marve finished 5-of-10 for 64 yards and rushed five times for 36 yards.
Calgary quarterback Bo Levi Mitchell, who missed the last three games with knee and ankle injuries, threw TD passes to Brad Sinopoli and Joe West to guide the Stamps to their third straight win.
Mitchell completed 18-of-28 pass attempts for 258 yards with the pair of TDS and two interceptions.
He said there are things the team has to work on, but he was impressed, as usual, by Cornish's effort.
"That's just who Jon Cornish is," Mitchell said of the winning drive.
"We've got a good O-line. We've got guys who are going to go out there and press it, make sure they get guys out of the way and create big holes."
Winnipeg running back Paris Cotton had touchdown runs of 35 and 10 yards, including one at 7:39 of the fourth quarter that squeezed Calgary's lead to 26-23.
Cotton, who had 14 carries for 108 yards, got the nod to start his second straight game this week — a move that led to RB Nic Grigsby asking for and receiving his release.
"I think everybody on that field gave everything they had, we just didn't do it," Cotton said.
"We didn't execute enough, that's what we're working on. I feel like this game is something to build off of."
Calgary backup QB Drew Tate had a one-yard TD run, while Stamps placekicker Rene Paredes booted a 41-yard field goal and punter Rob Maver had a pair of singles.
Winnipeg placekicker Lirim Hajrullahu was good on field goals from 26 and 29 yards and went wide on a 37-yard attempt that was brought out. He added a punt single and Calgary conceded a safety for another pair of points.
Calgary had a 14-0 lead by 8:34 of the first quarter and led 16-6 at halftime.
The Stampeders scored points on their first four possessions.
They began by efficiently using the game's opening drive to march from their own 41-yard line for Sinopoli's 25-yard TD catch at 5:54, a toss from Mitchell when Calgary was facing second-and-15.
Sinopoli was injured on the play and didn't return to the game. He said after the game he thinks he may have broke his collarbone.
Winnipeg's first possession was a two-and-out.
Calgary then started again from its own 41-yard line and the three-play, 69-yard drive was capped with West's 51-yard TD catch at 8:34 as he got behind the Bombers' defence and was wide open.
The Bombers responded with Hajrullahu's 26-yarder to make it 14-3 at 12:59.
Injuries hit the Bombers as they lost defensive lineman Greg Peach, defensive back Demond Washington and receiver Nick Moore. O'Shea didn't have updates on their conditions.
Calgary's fourth possession of the game ended with a punt single at 6:17 of the second quarter.
Winnipeg receiver Clarence Denmark's juggling 54-yard catch while fighting off defensive back Joshua Bell got the Bombers to Calgary's eight-yard line, but the highlight catch was for nothing.
Stamps defensive lineman Shawn Lemon forced Brohm to fumble and Calgary's Junior Turner recovered the ball at his own 17-yard line.
Calgary offensive lineman Brander Craighead was injured on the drive, which ended quickly when Bombers DB Chris Randle intercepted Mitchell. Craighead didn't return and there was no update on his condition after the game.
Winnipeg scored 10 points in the third quarter to close Calgary's lead to 23-16.
Paredes nailed 41-yard field goal at 4:18 of the fourth, but Cotton notched his second TD for the 26-23 score.
It was Calgary's 10th straight win over the Bombers. The teams meet again in Calgary on Nov. 1.