Celtic secured an eighth consecutive Scottish Premiership title with a convincing 3-0 victory over Aberdeen at Pittodrie Stadium on Saturday.
Striker James Wilson missed two early opportunities to put Aberdeen ahead before Neil Lennon's Celtic took the control of the match with the opening goal just before halftime.
The visitors doubled their eight minutes after the interval as McGregor's outswinging corner was met by a powerful header from defender Jozo Simunovic, who also scored the winner against Kilmarnock last weekend.
Striker Odsonne Edouard added a third goal shortly before the final whistle to extend Celtic's unbeaten run to 11 games in all competitions since Lennon took charge as a caretaker manager following Brendan Rodgers's departure for Leicester City.
"It's wonderful. Great moment for the players and the supporters, they are the most important people," Lennon said. "They gave me the heebie-jeebies there for a little bit today but we were magnificent in the second half.
"I've got to pay Brendan a huge amount of credit, because of the foundations that he laid. For me to be standing here as interim manager, or any kind of manager on a day that we win the title, is very special for me and my family."
The Glasgow side's sixth consecutive win at Pittodrie means they are now 12 points clear of second-placed Rangers who have three games to play.
Celtic, the League Cup winners, could complete a third successive domestic treble when they meet Hearts in the Scottish Cup final on May 25.