Wycombe were troubled by Posh's early pace and had a couple of narrow escapes before Craig Mackail-Smith broke the deadlock on eight minutes, latching on to George Boyd's quickly taken free-kick and slotting a measured shot to the left of goalkeeper Jamie Young.
Lewis Christon rescued Wycombe by dispossessing Mackail-Smith with a superbly timed tackle after Young fumbled a punt up field by Posh defender Craig Morgan. This was the signal for the visitors to up their game and force their way in front.
Wycombe's two first-half goals both came from wickedly swerving corner kicks by Chris Palmer, the first after the defender had brought a one handed diving save from Mark Tyler.
The Posh keeper flapped at Palmer's flag-kick from the right and a goalmouth scramble ended with Matt Bloomfield forcing in a 23rd-minute equaliser.
Six minutes later Palmer curled the ball over from the opposite flank and with Posh again caught out, Sam Stockley buried a shot from 10 yards after Bloomfield headed back from the far post.
It was a different story after the break when Posh, with the wind at the backs, regained the advantage.
Micah Hyde picked out Adam Newton with a defence-splitting pass before the defender netted his first of the season on 59 minutes. And Posh went in front on 75 minutes with Mackail-Smith holding off Stockley before beating Young from the edge of the area.
But Wycombe savaged a point through the cool-headed Mooney who put away the 86th minute spot-kick after Ben Futcher had brought down Tommy Doherty.