James Dornelly made his league debut as Posh recorded a 2-0 victory at Bristol Rovers to confirm that they will finish no lower than fourth in the table.
Technically, Posh could still finish second, but it would take a monumental swing in terms of goal difference for that to happen, so Darren Ferguson's will finish in the play-offs and will await their opponents with interest after a 2-0 victory at Bristol Rovers consolidated their position in fourth spot in the table.
The first half display was full of excellent passing football for which Posh fans are accustomed too, while in the second, they dug in to get over the line with substitute Ricky-Jade Jones providing a stoppage time second goal after Joel Randall had given Posh the lead in the first period.
Malik Mothersille, who excelleed playing from the left, had the first opportunity of the game, cutting inside onto his right-foot inside the opening three minutes, but his shot was routine for Ward.
Three minutes later, Ward produced heroics to keep out a combination of Posh players from close-range as Rovers struggled to clear.
Mothersille couldn't divert a shot back across goal at the back post on 21 minutes before the deadlock was broken on 40 minutes as good work from Mothersille down the left created the chance for RANDALL and he guided his volley into the back of the net to give Posh a deserved lead.
Steer made a routine save to keep out a cushioned volley from Evans on 49 minutes before the keeper made a brilliant stop to keep out Sinclair after he had found room in the box.
Steer kept out a first-time effort from substitute Vaughan on 78 minutes before Josh Knight was cautioned for time wasting.
A second goal arrived deep in stoppage time and it was another assist for Harrison Burrows as his low centre was cleverly flicked into the net by Jones.
Posh go to Cheltenham Town on Tuesday night with manager Darren Ferguson confirming he will freshen the entire team up for that clash.
Bristol Rovers: Ward, Sinclair, Aguilera (sub McCormick 71min), Thomas (sub Vaughan 71min), Rossiter (sub Conteh 51min), Taylor (sub Connolly 5min), Vale, Brown, Evans, Baggott, Hoole (sub Hunt 71min). Unused subs: Hall, Connolly, Gordon,
Posh: Steer, Burrows, Edwards, Knight, Dornelly (sub Katongo 63min, sub Crichlow 84min)), Kyprianou, Collins, Randall, Ajiboye, Mothersille (sub Mason-Clark 70min), Clarke-Harris (sub Jones 70min). Unused subs: Bilokapic, De Havilland, Wakeling.
Half-time: Bristol Rovers 0-1 Peterborough United
Full-time: Bristol Rovers 0-2 Peterborough United
Attendance: 8,714 (602 Posh fans)
Referee: Tom Reeves