Posh Pegged Back For Draw At The ABAXOn Boxing Day, it was Gillingham that provided the last blow as Justin Edinburgh's men secured a point with a last gasp volley from Baily Cargill to cancel out Lee Angol's opener.
McGee was called upon inside the opening two minutes to deny the skilful Bradley Dack after the highly-rated midfielder had nutmegged Michael Bostwick over on that far side.
The Posh shot-stopper was called into action again on eight minutes to deny a low Emmanuel-THomas effort as Posh found themselves pegged back in the opening exchanges.
At the other end, a well worked Posh corner kick routine ended with the ball at the feet of Andrew Hughes, but he fired over with his right-foot from the ede of the box.
Two superb deliveries from Marcus Maddison created chances for Tafazolli, his first header was somehow kept out on the line by Ehmer and then he planted a header wide of the target from 10-yards.
In between those efforts, Maddison had seen a powerful cross-shot beaten behind by goalkeeper Nelson.
Edwards saw a powerful drive gathered by Nelson on 12 minutes with Coulthirst also seeing a shot blocked. The best chance of the opening quarter arrived on 13 minutes as an excellent reverse pass from Edwards found Nichols, but the former Exeter man took it first time and curled wide with his left-foot.
McGee produced a superb stop to tip a fierce Wagstaff effort from 25-yards as the open nature to the contest continued.
Maddison floated a free-kick over the bar on 29 minutes after he himself was hauled down on the edge of the box.
One minute of added time was signalled by the fourth official, but that passed by without incident. Edwards fired wide of the near post moments after the re-start after a glorious turn on the half way line.
Nichols had a great chance to break the deadlock on 49 minutes, his initial effort was saved by the legs of Nelson and then he fired the rebound wide as it bounced kindly back into his pat.
As good as the Nichols chance was, Gillingham squandered one just as clear cut moments later as Emmanuel-Thomas scooped a shot over the bar after a low corner kick picked him out in space.
Nichols had another go on 52 minutes, this chance a lot more difficult, his curler slicing horribly wide after good work from Da Silva Lopes.
Posh made their first change on the hour mark with Lee Angol replacing Coulthirst. George Moncur replaced Maddison as McCann made his second change.
Angol fired wide with his left-foot from 25-yards as Posh pushed for the breakthrough. That breakthrough arrived on 77 minutes, a perfect cushioned pass from Nichols found substitute ANGOL, his first shot was blocked but he rifled home the rebound in off the far post.
McGee was called upon on 84 minutes to deny a deflected effort from Dack as the Gills pressed for an equaliser.
In the final seconds, Gillingham found an equaliser as a cross into the box was guided past McGee by CARGILL to break Posh hearts.
Posh: McGee, Smith, Hughes, Bostwick, Tafazolli, Edwards, Forrester, Maddison (sub Moncur 66min), Coulthirst (sub Angol 59min), Da Silva Lopes, Nichols (sub Oduwa 90min). Unused subs: Tyler, Angol, Almeida Santos, Inman, Binnom-Williams.
Gillingham: Nelson, Jackson, Ehmer, Wagstaff, Hessenthaler (sub Donnelly 85min) McDonald (sub Nouble 72min), Konchesky, Cargill, Dack, Wright, Emmanuel-Thomas. Unused subs: Hadler, Oshilaja, Knott, Byrne, Oldaker.
Half-time: Peterborough United 0-0 Gillingham
Full-time: Peterborough United 1-1 Gillingham
Attendance: 6,239 (420 Gillingham fans)