Okoli gave the visitors a shock lead when he got in front of Boro defender Luke Ayling to head home Divine Mukasa’s right-wing free-kick.
But defender Okoli gave the ball away in the build-up to the hosts’ equaliser just before the interval.
Boro sprang forward and Hayden Hackney played the ball to the left to Tommy Conway, who pulled it back for McGree to tuck away his third goal in his past four matches.
Leicester had a great chance to regain the lead early in the second half, when Ayling’s botched attempt to head away a long ball left Patson Daka one-on-one with keeper Sol Brynn, but the striker headed wide.
Leicester continued to threaten and Abdul Fatawu sent an effort narrowly wide of the far post.
At the other end, Callum Brittain’s cross was nudged narrowly wide by David Strelec, Conway fired well over, and veteran keeper Asmir Begovic saved with his legs to deny McGree.
After a recent defeat by Coventry saw the Sky Blues regain top spot from Boro, Kim Hellberg’s side have dropped points against two teams battling against the drop, having played out a frustrating goalless draw against Oxford United at the weekend.
They are six points clear of third-placed Ipswich and Hull in fourth, but will be keen to get back to winning ways in their next match, away to Birmingham on Monday.
Leicester, who are at home to Norwich on Saturday, remain third from bottom and are without a win in eight league matches.
But they are just a point behind West Bromwich Albion, the team immediately above them in the table, and their performance suggested they are capable of getting out of trouble under Rowett.