McGowan was rewarded for his recent form in Neil Lennon’s Development Squad with his first Hoops start in the SPL.
"In my mind he has cemented his place in the first team squad so let's hope he can push on," the Hoops boss told the club's official web site. "His overall performance pleased me. He is a young guy who deserves an opportunity.
"Every day in training you see he has a great enthusiasm for the game and he is good off both feet so I'm delighted for him."
In defence, 19-year-old Thompson continued to excel by also scoring as Celtic kept their third clean sheet in a row.
"It's always good for a young player to score his first goal. It's something he will always remember," said the manager.
"But we are all more pleased with the clean sheet rather than the goal. He is going to build his career on clean sheets rather than goals.
"For a young guy who has just turned 19, he has done exceptionally well and I'm delighted that he is progressing the way he is."