Russell Slade's leaders fell behind against the run of play when Grant McCann's free-kick was diverted in by Posh skipper Tommy Rowe after 26 minutes, but it did not take them long to turn the contest around.
The excellent David Mooney fired a warning shot when thumping a volley against the crossbar, but not even the woodwork could come to Posh's rescue when he beat Bobby Olejnik with a 38th-minute shot on the turn after strike-partner Kevin Lisbie had steered a cross into his path.
Both forwards were involved in the build-up as Dean Cox stylishly swept Orient ahead four minutes after the break when clipping the ball over Olejnik.
The points were in the bag in the 58th minute when Mooney collected a pass from Cox and flashed a low drive across Olejnik to register his 11th goal of the campaign
Kevin Doyle and James Henry kept Wolves' promotion push firmly on course as they ground out a 2-0 League One success against Stevenage at Molineux.
Wolves made it an impressive 11 wins from their last 13 league games with a goal in each half as Boro saw their run of three wins in four league matches come to an end in the first ever meeting between the sides.
But it was tough on the visitors who found themselves frustrated by a man-of-the-match display from Wanderers goalkeeper Carl Ikeme.
Joe Garner's last-gasp header earned high-flying Preston a 1-1 draw against struggling Tranmere who still forced their way out of the relegation zone.
Everyone inside Deepdale stood to applaud in the seventh minute in tribute to Tranmere midfielder Joe Thompson who was diagnosed with cancer this week.
Rovers took the lead in the 55th minute when Chris Atkinson latched on to Max Power's through ball and shot calmly past Declan Rudd.
But Garner notched his second league goal of the season on the stroke of full-time, heading home Chris Humphrey's cross.
Coventry climbed into top half for the first time this season with a 3-0 thrashing of 10-man Notts County.
The managerless Magpies were holding the in-form Sky Blues heading to half-time until Danny Haynes was shown a straight red card in the 41st minute for a high tackle on Jordan Clarke.
The dismissal changed the match's complexion as two goals from Leon Clarke and a Callum Wilson strike helped the hosts to a healthy win.
Swindon got back to winning ways after Massimo Luongo and Dany N'Guessan inspired a 5-2 demolition of Port Vale.
Mark Cooper's Robins had lost their last two fixtures but a Luongo brace and goals from N'Guessan, Nile Ranger and Nathan Byrne ensured the lull was shortlived.
An early penalty from Adam Forshaw proved enough to secure in-form Brentford a 1-0 victory over Crawley whilst fellow promotion hopefuls Bradford were held to a goalless draw at Crewe.
Elliot Lee's dramatic injury time header earned Colchester a point at Rotherham with Bristol City and Oldham also sharing the spoils.
Elsewhere, there were wins for Shrewsbury and Gillingham against Sheffield United and Carlisle respectively.