The O's have yet to lose this season and remain top of English football's third tier, while the Posh, one point behind in second place, recorded their fifth consecutive win
Orient remain one point clear at the top of the table after coming from behind to defeat Karl Robinson's side 2-1.
Patrick Bamford put the losers in front on the half-hour mark with his 11th goal of the season in all competitions, but Moses Odubajo levelled proceedings just before half-time with a curling left-foot strike.
|LEAGUE ONE RESULTS
Tyrone Barnett scored the only goal of the game four minutes from time as second-placed Peterborough beat Port Vale 1-0.
The Posh looked like being frustrated at Vale Park but Barnett had other ideas, finishing off a one-two with a powerful left-foot effort past Port Vale goalkeeper Chris Neal.
Sheffield United slipped to the bottom of the table on Sunday after losing 3-2 at Coventry City. The Sky Blues raced into a 3-0 lead, with Leon Clarke scoring either side of Callum Wilson's strike. The Blades, playing under caretaker boss Chris Morgan after David Weir was sacked on Friday, hit back twice Lyle Taylor but could not salvage a point.
Their misery was compounded when Tranmere Rovers picked up their first win in six league matches at the expense of Bradford.
Striker Ryan Lowe proved to be the hero for Ronnie Moore's men as he bagged the winner 24 minutes into the second half.With Bradford losing and Wolves not playing due to international call-ups, there was an opportunity for the teams just below Orient and Posh to make up ground on Saturday.
But Preston were consigned to a surprise 2-0 home defeat by lowly Crewe Alexandra to lose their unbeaten home record.
Byron Moore opened the scoring with a clever effort in the 27th minute before a stunning curling strike from Bradden Inman sealed the result.
The win was Crewe's first league triumph in eight attempts and moved them out of the relegation zone.
Rotherham United also slipped up, with Swindon Town hammering them 4-0 at the New York Stadium to post their first away win in the league since March.
Tottenham loanees Alex Pritchard and Massimo Luongo scored before the break for Swindon, who sealed their victory thanks to second-half efforts from Nicky Ajose and Dany N'Guessan.
Stevenage recorded only their second league win of the campaign, with Francois Zoko bagging a double in a 2-1 success over Brentford.
A last-gasp equaliser from Andy Taylor denied Colchester United a first league win in nine matches as Walsall snatched a 1-1 draw, with Freddie Sears on target for the home side.
In the other game in League One on Saturday, Shrewsbury Town secured a 2-0 home win over Gillingham courtesy of goals from Joe Jacobson and Liam McAlinden.