Coventry extended their unbeaten league and…
Milan Van Ewijk then fired the Sky Blues in front after 87 minutes before O’Hare wrapped up all three points with his second in injury time.
The Foxes were a man down from the 45th minute following Abdul Fatawu’s challenge on Jake Bidwell.
Coventry extended their unbeaten league and cup run to nine games after handing Leicester only their fourth defeat of the season – to end the Foxes’ 10-game unbeaten run.
The Sky Blues had won only once in 18 league meetings with Leicester – a 2-0 win in the days of Chris Coleman as Coventry boss in February 2008.
But, on Leicester’s first league visit to Coventry since the opening day of the 2011-12 Championship season, when they won 1-0 with a goal by Lee Peltier, the Foxes were this time in for a shock.
They survived an early let-off when O’Hare won the ball back and Tatsuhiro Sakamoto cut in from the right to test Mads Hermansen with a fierce shot which the Leicester keeper did well to turn onto his left upright and to safety for a corner.
But Coventry looked the better side in an engaging first half which brought a dramatic climax, when Leicester went one up, only to then immediately go a man down.
Bobby Thomas put in a fair challenge that took the ball, which bounced out for what should have been a goal-kick off Dewsbury-Hall’s chest. But referee Darren England surprisingly chose to award a penalty.
Dewsbury-Hall converted the spot-kick for his third goal against Coventry this season, having scored twice when the Foxes came from behind to win 2-1 on the opening weekend of the season at the King Power Stadium.
Then came the second moment of controversy when Fatawu’s sliding tackle on Bidwell was deemed worthy of a straight red card.
With the whole of the second half ahead of them, Coventry were now in the box seat as they strove to avoid what would have been only a second home defeat of the season. But chances did not come as readily as they might have hoped.
Sakamoto and Van Ewijk opened up Leicester down the right – but Matt Godden’s powerful header was too close to Hermansen.
It took until 11 minutes from time for an equaliser to arrive. O’Hare showed some artful footwork in the Leicester box to outwit Wout Faes and thread a low right-foot equaliser through the nutmegged Foxes defender’s legs.
Then Van Ewijk brought the 29,914 full house down as he chanced his arm from 20 yards out and it bobbled into the left corner. And there was even still time for a cake-icing second for O’Hare.
Coventry now face successive away trips to Hillsborough to play Sheffield Wednesday in the league next Saturday before returning the following Friday to face the Owls in the fourth round of the FA Cup.
Enzo Maresca’s Foxes have nine days to recover ahead of the first of three successive home games.
They host second-placed Ipswich Town on Monday 22 January, before facing the winners of the Birmingham City-Hull City FA Cup third-round replay the following Saturday.
They then host Swansea City on Tuesday 30 January.
Coventry City matchwinner Callum O’Hare told BBC CWR:
“Massive scenes. We’re buzzing. We wanted to prove how good we are.
“They’re top of the league by a mile – and we wanted to show we deserve to be up there.
“It looked to me like Bobby Thomas had won the ball for their penalty.”
Coventry City boss Mark Robins on O’Hare, whose current deal expires in the summer:
“You’ve got to wait for that. We can only do so much but we will 100% want to keep him. Whatever happens it won’t be for the want of trying or not wanting to do it from our part.
“Looking at characteristics of people in teams, he epitomises what we want to do. He is brave, goes after things, a good communicator, an effervescent character and has added goalscoring to it. He deserves all the plaudits he gets. We missed him greatly.
“We were brilliant. It was one of the best performances we’ve had this season, in many seasons. You have to understand how good the opponents are and then pick the bones out of it. Even with 11 v 11 we were outstanding.”
Leicester City boss Enzo Maresca told BBC Radio Leicester:
“The red card completely changed the game. I prefer not to talk about the referee.
“It is what it is. The second half changed completely. With one less player it is not so easy to continue the way we were playing.
“We do not like to drop points. But it is just a normal defeat. We will analyse it and try to turn it round next game.”