The keeper had a game to forget the last time the Parkhead side visited Ibrox on league business back in January as he gifted them an opener in their 2-0 win.
But after Georgios Samaras’ double that day, McGregor exorcised his demons in style as he made a magnificent stop against the Greek hitman from 12 yards in this match.
Earlier in the game, the Scotland star had to save from Daniel Majstorovic and Emilio Izaguirre to keep the score sheet blank.
But denying Samaras eight minutes from full time was arguably more crucial as the incident came at a time when it appeared Celtic might just sneak this derby.
The Light Blues were the better team in the first half and had chances to forge ahead themselves in the early stages of the second.
Neil Lennon’s side responded well though and could have edged it instead in the closing stages.
The 0-0 draw – the first in Govan between the teams since the Dick Advocaat era – means Rangers stay top of the league with just four games of the championship to go.
But Celtic are a point behind them and with one more fixture to play, they are in control with the title race looking like it will be settled on the final day of the competition.
All Walter Smith’s men can do now is hope they win against Motherwell, Hearts, Dundee United and Kilmarnock in the next three weeks.
After that, they’ll need to rely on a favour from one of Celtic’s opponents in the final throes of the campaign to turn things on their head again.
Smith made just one change to the side which had won 4-0 against United at Tannadice, with Gregg Wylde replacing Kyle Hutton.
That meant the Light Blues began with the same outfield players who had kicked off the League Cup final last month, with McGregor in goals rather than Neil Alexander.
The hosts made a bright start, with Izaguirre having to react well to head behind a dangerous Wylde cross as he tried to set up an early goal.
At the other end, a foul by Madjid Bougherra on Samaras led to a corner from the free kick but it was eventually dealt with by McGregor.
There was a pulsating atmosphere within the stadium and that made for a furious reaction to every foul committed.
But while previous Old Firm clashes have led to early bookings as a result, referee Craig Thomson resisted the temptation to issue any cautions in the opening exchanges.
Play was swinging from end to end and a surging run and teasing centre from Steven Davis led to confusion in the away rearguard before the ball was scrambled clear.
Nikica Jelavic was then denied after Kyle Lafferty got up superbly to win a flick on and Maurice Edu also saw his drive deflected behind rather than in.
Jelavic and Lafferty were linking ever so well and were causing all sorts of problems for the Parkhead outfit.
A blatant foul on the Croat by Beram Kayal – who, despite Thomson’s desire to keep his book in his pocket was coming closest to changing that – gave Gers a chance to score.
But Jelavic blasted into the wall before a flashpoint in McGregor’s penalty area led to the first two yellows of the contest.
Samaras went in late on the keeper and after he was brushed away by David Weir, the former Manchester City player reacted with a two-handed shove on the veteran defender.
By the letter of the law he should have been sent packing but somehow stayed on the park – with Weir bizarrely given the same punishment.
Scott Brown had Celtic’s best chance yet as they began to settle into the game but he pulled his drive past the post before Steven Naismith did the same thing at the other end.
As the first half wore on, play became much more balanced and it was swiftly developing into a midfield battle.
There was certainly more impressive stuff going on there than at Gary Hooper’s feet and his attempt was so off target it landed in the upper tier of the Copland Road Stand.
With half-time approaching, there hadn’t been many chances for either side but Rangers had had more action in front of their opponents’ goal.
From that point of view, they will probably have been disappointed to go into the break with the scores still tied at 0-0.
It was to be expected Smith’s men would try to take the game to their rivals at the restart before they thought about throwing the likes of Kris Commons on to stretch play.
And both Weir and Naismith came close to breaking the deadlock, with the latter’s half volley goalbound before it was diverted behind for another corner.
Lafferty then contrived to head past the post from a perfect Wylde cross when his overall performance deserved so much more.
Kayal served a reminder the teams were still level when he nearly gave Celtic an advantage with a crisp hit from 25 yards that whistled wide.
Seconds later, a sensational save from McGregor kept out Majstorovic’s header just when it seemed to be creeping over the line as Celtic applied pressure.
Sure enough, Commons came on for pre-match doubt Joe Ledley and with that the away team started to edge forward a touch more.
But it was Gers who hit back and when a rampaging run was brought to an end illegally by Kayal, Lafferty’s free kick wasn’t far from going in.
The SPL champions were knocking on the door and good hold-up play by Jelavic released Naismith, who was within a whisker of scoring from the edge of the box.
On a real knife edge, the game could easily have gone either way as it rolled into the final quarter.
Hooper and Charlie Mulgrew could have struck for Celtic while McGregor had to shove a hand up once more to help Izaguirre’s shot over the woodwork.
Going into the final 10 minutes, it was the away team which was in the ascendancy as it peppered the Light Blues goal with one ball after another.
And when substitute Anthony Stokes won a penalty when he was fouled eight from the end, it seemed they would get their chance to sneak it.
But having made two wonderful stops already, McGregor once again launched himself in the right direction to fist away Samaras’ spot kick and keep his team in the match.
There were just moments left and both sides had a go at claiming the win, with substitute El-Hadji Diouf perhaps having the best opportunity to snatch it.
But as his free kick curled over the wall and inches by the upright, it was clear this one was destined to remain deadlocked and the championship is poised to go right to the wire.