Goals from Jonson Clarke-Harris and Jack Taylor helped Peterborough clinch the final play-off position with a 2-0 Sky Bet League One win at Barnsley.
Darren Ferguson’s side will face Sheffield Wednesday in the play-off semi-finals, with Barnsley facing Bolton.
Posh took the lead inside six minutes at Oakwell through main man Clarke-Harris. Ephron Mason-Clark’s ball from the left found the club’s top scorer, who fired home from inside the box.
James Norwood thought he had equalised in the 15th minute but the linesman had raised his flag for offside.
The Reds came close again on the hour mark when Luca Connell’s corner was headed narrowly wide by Liam Kitching.
Peterborough’s Taylor had a brace of chances five minutes later to double his side’s lead but could not get the better of goalkeeper Harry Isted.
Visiting keeper Will Norris was called into action in the 69th minute when Josh Benson’s cross found the head of substitute Slobodan Tedic, whose effort was tipped around the post.
Peterborough doubled their lead in the 76th minute when Taylor headed home from Harrison Burrows’ corner – and when news of Derby’s loss at Hillsborough was confirmed, the away fans at Oakwell could look forward to play-off action.
