Darren Ferguson's men were beaten by a lively Coventry City side at Sixfields as the excellent recent run in Sky Bet League One was brought to a shuddering halt by Stephen Pressley's free-scoring side.
Inside the opening four minutes, Posh created a great opportunity as Anderson worked the ball to Ntlhe, his shot was parried by Murphy with Ephraim scuffing the rebound wide of the target.
Posh had the ball in the back of the net on 14 minutes as Assombalonga tapped home from close-range following a low Tomlin cross, but the offside flag curtailed the celebrations.
The deadlock was broken on 20 minutes as a clever McCann free-kick was headed towards goal by Brisley, the effort was parried and when the ball was recycled, JEFFERS was there to pounce to give Posh the lead against his former club.
Olejnik produced a good stop to deny Christie's curler before Assombalonga fired wide of the near post as the open nature of the first half continued.
The lively Clarke clipped the top of the crossbar with a 25-yard free-kick after Brisley had been penalised for a foul on Wilson.
In stoppage time, Coventry were gifted an equaliser as a back pass from Brisley was cleared poorly by Olejnik and CLARKE fired into an empty net.
However, the lead lasted less than 60 seconds as TOMLIN made room in the box superbly, his initial shot was parried by goalkeeper Murphy, but the Posh striker buried the rebound.
Three minutes into the second half, the Sky Blues were level again as a corner was not dealt with by Olejnik or the defence and CLARKE rifled home from 10-yards.
Fleck was denied by goalkeeper Olejnik moments later before Wilson flashed a shot from the edge of the area well wide of the target.
Baker somehow missed from two-yards with only Olejnik to beat on the hour mark, the goalkeeper getting a touch, but it looked harder to miss than score.
Wilson then had the ball in the net as Olejnik spilled a swerving Fleck effort, but the offside flag curtailed the celebrations.
On 68 minutes, Olejnik denied a low drive from the lively Moussa. Olejnik produced a fine stop to deny Seabourne's header from a free-kick from the right by Baker while the latter scuffed a shot wide of the target.
Shaun Jeffers was replaced by Nathaniel Mendez-Laing on 77 minutes. Two minutes later, the Sky Blues were in front as static defending at the back allowed Clarke to find MOUSSA who fired the ball past Olejnik and into the back of the net.
Tyrone Barnett was thrown into the fray with five minutes of normal time remaining by boss Darren Ferguson. Substitute Dagnall fired wide of the far post on 87 minutes.
Posh felt they should have been level when Mendez-Laing's cross was turned in at the far post by Brisley, but the lineswoman Amy Fearn failed to spot it as Murphy clung the ball away from danger.
With Posh furious at the injustice, they were caught at the other end as WILSON raced clear and fired high and into the roof of the net past Olejnik.
Final Score: Coventry City 4-2 Posh
Coventry: Murphy, Christie, Adams, Webster, Thomas, Fleck, Baker (sub Dagnall 77min), Clarke, Moussa (sub Phillips 85min), Seabourne, Wilson. Unused subs: Burge, Barton, Daniels, Willis, Dagnall, Haynes.
Posh: Olejnik, Little, Ntlhe (sub Barnett 84min), Brisley, Bostwick, McCann, Anderson (sub Ferdinand 66min), Ephraim, Tomlin, Assombalonga, Jeffers (sub Mendez-Laing 77min). Unused subs: Day, Payne, Swanson, Mendez-Laing, Knight-Percival, Barnett.
Attendance: 4,905 (2,202 Posh fans)