Toronto backup quarterback Michael Bishop (left) and Arland Bruce III smile as they leave the field after defeating Winnipeg on Sunday. ((Adrian Wyld/Canadian Press))

Backup quarterback Michael Bishop came off the bench in the fourth quarter to lead the Toronto Argonauts to a 31-27 victory over the Winnipeg Blue Bombers in Sunday's East Division semifinal.

Bishop threw a pair of touchdowns within a two-minute span midway through the fourth to erase a 10-point Winnipeg lead and guide the Argos to a thrilling come-from-behind win before a boisterous crowd at Toronto's Rogers Centre.

"As a backup quarterback you never know when you're going to have an opportunity," Bishop said. "I have to be hot when I come in and I was [Sunday]."

Toronto faces the Alouettes in Montreal in next Sunday's East Division final (CBC, 12:30 p.m. ET).

If they can beat the Alouettes, the Argos will head to the 94th Grey Cup game at Winnipeg's Canad Inns Stadium on Nov. 19 (CBC, 5:30 p.m. ET).

"We felt we should've beat them last week," said Argos running back Ricky Williams. "I'm sure they have something for us but we'll have something for them."

Argos starting quarterback Damon Allen struggled to find his rhythm and came out of the game after he was hit hard by Winnipeg's Doug Brown midway through the fourth.

"[The Bombers]have different strengths and so the way Michael attacks a defence is different from the way Damon does," Clemons said. "Sometimes it's a game like this that really helps to build momentum."

Despite the change, Clemons said Allen will start against the Alouettes.

Williams said Bishop gave the Argos offence a big lift the moment he stepped onto the field.

"He's probably the best athlete on the team," Williams said. "So when he gets into the game I think people get excited because of his athletic ability."

Winnipeg quarterback Kevin Glenn, who hurt his ankle in last week's season-ending loss to the B.C. Lions, overcame a poor first half with a strong effort over the last two quarters.

CFL rushing champion Charles Roberts ripped apart the Argos' defence, rushing for 176 yards and two touchdowns, but he also gave up the fumble that led to Toronto's winning touchdown.

"It was a clean strip but I really didn't have control of the ball from the handoff," Roberts said. "It probably wasn't smart but I tried to fight for yards instead of going down.

"It's unfortunate that we — I mean, I — turned the ball over. Once you've got the lead you've got to hold on to the ball."

Toronto led 7-3 early in the second quarter on the strength of two field goals from kicker Noel Prefontaine. Winnipeg's Troy Westwood booted a short field goal to make it a one-point game, before Toronto took a 14-6 lead when Allen threw a 23-yard touchdown to Michael Palmer with 1:26 left in the half.

The Argos had the ball on Winnipeg's 17-yard line after Glenn was intercepted, but Allen was picked off in the end zone by Blue Bombers linebacker Kyries Hebert, thwarting Toronto's chances of extending its advantage going into halftime.

Winnipeg's offence finally came alive in the third quarter, as Roberts continued to run the ball effectively and Glenn started hitting his receivers.

The Blue Bombers put together a long drive, capped off by Roberts' one-yard touchdown run with 3:31 left in the third quarter. Two minutes later, Glenn completed a 60-yard pass to veteran receiver Milt Stegall, setting up an 11-yard touchdown scamper by Roberts to put Winnipeg ahead 20-13.

Prefontaine's 38-yard field goal early in the fourth cut Winnipeg's lead to three points, but Glenn went right back to work on the ensuing drive and tossed a 27-yard touchdown pass to Chris Brazzell in the end zone to make it 27-17 for the Blue Bombers.

With Allen struggling, Bishop came into the game in the fourth quarter and made an immediate impact, throwing touchdowns to Arland Bruce III and R. Jay Soward 1:45 apart to put Toronto ahead 31-27.

Winnipeg drove to the Toronto 31-yard line with under a minute left, but Argos safety Orlondo Steinauer intercepted a pass from Roberts with 44 seconds remaining to cement the victory.

With files from the Canadian Press