The 21-year-old has been the highlight for the Hoops this season, with a number of bright displays - including scoring in Champions League qualifiers against Legia Warsaw and NK Maribor - characterising his meteoric rise to prominence in the club's ranks.
Parkhead manager Ronny Deila admitted earlier this month that the star, who was called up to Gordon Strachan's Scotland squad this week, had surprised him with his attitude and ability.
It's clear that bosses at the club also agree with the Norwegian, and today's news will come as light relief to the Parkhead masses following Tuesday's Champions League exit.
McGregor struck the bar in that 1-0 defeat to Maribor, while his directness and creativity offered some hope to the Hoops on a bleak night at Celtic Park.
A product of the Celtic Academy, McGregor spent a loan spell with Notts County last season, netting 14 times for the League One outfit before returning north to Glasgow in the summer.
Speaking earlier this week about the midfielder, Scotland boss Strachan said: "At Notts County Callum was playing with guys who had to win to receive a bonus to make a difference to their lives. He had to stand in front of 5,000 to 6,000 people who boo and scream if he hits a bad pass. Can he come back from that?
"That is a reality and he has dealt with reality. He could have sat there, walking about Glasgow saying, 'I'm a Celtic player'.
"But Callum chose to go to Notts County because he wanted to learn the game. I like that. Character is needed in football. You can have all the skill but character is a huge thing.
"Playing in Europe has helped him but so did going to Notts County. He did that himself. Callum has decided what his future is going to be, no one else."