With Reese McGuire standing on second base, Joe Panik popped out on a bunt attempt and Cavan Biggio lined out. But Grichuk followed with his ninth homer, a drive to straightaway center on a 1-0 pitch by Cole Sulser (1-3).
''I barreled it well,'' Grichuk said. ''My hands kind of got away from me a bit. I knew it had a chance.''
Baltimore had taken a 4-3 lead on Hanser Alberto's bloop RBI single against Rafael Dolis (1-1) in the top of the 10th. Alberto had four hits and Renato Nunez homered for the Orioles in their third straight loss.
Vladimir Guerrero Jr. and Teoscar Hernandez hit back-to-back homers for Toronto, which improved to 4-5 in extra-inning games. Dolis earned his first big league win since May 6, 2012, with the Chicago Cubs.
''We've had a lot of one-run games and we've blown a couple late and we've won a couple late,'' Grichuk said. ''It's setting us up to be in a good place late in the year.''
The clubs commemorated Jackie Robinson Day by having all team members wear uniform number 42, an annual observance normally conducted on April 15 but moved this year because of the COVID-19-altered schedule.
The homers by Guerrero and Hernandez opened the scoring in the fourth, but Baltimore tied it when Ryan Mountcastle reached on a bases-loaded infield single in the sixth, driving in two runs.
Guerrero extended his hit streak to 10 games. Hernandez's 12th homer matched Chicago's Jose Abreu for the American League lead.
Toronto went up 3-2 when Guerrero scored on a wild pitch in the bottom half of the sixth, but Nunez tied it again with a drive off Jordan Romano in the eighth.
Romano left the game one pitch later with an injury to the middle finger of his pitching hand.
Grichuk also made a diving catch in the first, ranging to his right from center field to rob Anthony Santander. He then batted in the bottom of the inning and grounded out, but not until the 11th pitch of an at-bat that featured six foul balls against John Means.
Grichuk went 2 for 5 to raise his batting average to .311. He had a .244 career average coming into the season.
''He's making more contact,'' Toronto manager Charlie Montoyo said. ''He's been way better than last year, locked in and putting the ball in play.''
Orioles: C Pedro Severino (hip flexor) and SS Jose Iglesias (left quadriceps strain) both started, with Iglesias in the lineup at DH. Severino had been day to day and Iglesias came off the IL on Thursday. ... Manager Brandon Hyde said RHP Hunter Harvey (right forearm strain) would likely see action ''toward the end of the series,'' which runs through Monday.
Blue Jays: Montoyo said closer Ken Giles (forearm strain) threw on the side and felt good, adding that the next step is throwing live BP. ... RHP Nate Pearson (elbow tightness) played catch from 60 feet and will be extended to 90 and 120 feet over the next few days before throwing a side session ... SS Bo Bichette (knee sprain) started swinging off a tee Thursday and also played catch.
Orioles: RHP Alex Cobb (1-2, 3.73 ERA), who has held opposing batters to a .220 average, will start Saturday in the second game of the four-game series.
Blue Jays: RHP Taijuan Walker (2-2, 4.00 ERA) will make his Toronto debut Saturday. He was acquired in a trade with Seattle on Thursday to help bolster a rotation beset by several injuries.
More AP MLB: https://apnews.com/MLB and https://twitter.com/AP-Sports
Copyright 2020 STATS LLC and Associated Press. Any commercial use or distribution without the express written consent of STATS LLC and Associated Press is strictly prohibited.