Barnsley raced into a two-goal lead this evening but were pegged back by their hosts at London Road.
Goals from Herbie Kane and Devante Cole in the first half an hour of this one looked to have Neill Collins' side on the road to victory but a stubborn Posh outfit fought back to claim a share of the spoils.
The Reds were fast out of the blocks with Adam Phillips beating his man down the right wing inside the opening 60 seconds before seeing his cross drop kindly for Jordan Williams whose powerful shot, struck first time flew just inches over the crossbar.
It was all Barnsley in the early stages and only some last-ditch defending prevented goal-bound Luca Connell and Devante Cole strikes. But the goal their play deserved did arrive on 10 minutes.
Posh goalkeeper Nicholas Bilokapic received a backpass and his touch was heavy, allowing John McAtee to nip and nick the ball that slid across to Herbie Kane around 12 yards from goal and he buried the finish, low and hard into the bottom left corner.
Bilokapic had to be replaced soon after by Fynn Talley for the hosts.
We'd double our lead 31 minutes into the contest when Corey O'Keeffe robbed his man on the right flank before finding McAtee whose low cross was slammed home by Cole, six yards from goal.
The home side had a succession of corners in response but the clear-cut opportunities weren't forthcoming. However, they'd claw their way back into proceedings deep into added time at the end of the first 45 as Jonson Clarke-Harris' near post header was saved on the goalline by Liam Roberts, but Williams' attempted hooked clearance found only the back of his own net.
On the stroke of half time, Kane's improvised volley forced Talley to parry away but only into the path of Phillips with the Reds midfielder unable to keep his shot down, clearing the bar comfortably from just inside the box.
HALF TIME: Peterborough United 1-2 Barnsley
Barnsley were caught napping three minutes into the restart as Clarke-Harris powered home a header all too easily to level up the tie.
But the response was decent, with the Reds hitting Posh down the left flank as Cole raced clear of his marker before laying the ball perfectly into the path of the arriving O'Keeffe, but Corey's first-time effort on the run cannoned off the underside of the bar and away to safety.
Connell was next to try his luck, from the edge of the box, but Talley was sharp at his near post to turn the ball behind.
The same player soon saw a goalbound strike diverted inches wide by Ronnie Edwards as Barnsley maintained their dominance, but Mason-Clark would again show how dangerous Posh were on the break as he clipped the woodwork from an acute angle.
Chances were few and far between in an absorbing end to the fixture, where sub Ricky-Jade Jones had the final opportunity, scampering through one on one, only to be denied by Roberts who got their just in time.
FULL TIME: Peterborough United 2-2 Barnsley
Roberts, O'Keeffe (Łopata), Williams, de Gevigney, Dodgson, Styles, Kane, Connell, Phillips (Watters), McAtee (Cadden), Cole.
Unused: Killip, Cotter, Cosgrove, Jaló.
