Josh Low was adjudged to have pushed Wycombe top-scorer Scott McGleish in the box and the veteran marksman picked himself up to coolly fire the resulting spot-kick past Joe Lewis.
It looked as if the Posh were set to take all three points after substitute Liam Hatch had headed home Dean Keates' cross in the 84th minute as the visitors produced a stirring second-half fightback.
They had found themselves a goal down from the first shot of the game in the fifth minute. Leon Johnson was bundled over 25 yards out by Charlie Lee and Stefan Oakes curled a spectacular shot over the wall and into Lewis' top left-hand corner.
Oakes almost repeated the trick four minutes later, this time his inswinging free-kick was parried away at this near post by Lewis.
Peterborough came out a different side in the second half and showed exactly why they are challenging for the title.
Firstly they had a good shout for a penalty in the 52nd minute when Wycombe defender Leon Johnson appeared to handle Keates' goalbound shot and then Aaron McLean fired narrowly over after seizing on to Russell Martin's clearance.
Lee then forced Frank Fielding into a smart save before the best move of the match saw Posh grab their equaliser.
A six-pass sequence found Hatch in space and he fed George Boyd, whose shot was deflected inside the near post by Johnson.