Goalless at the half-way stage in this entertaining clash which would benefit from some added spark from two sides each gunning for promotion.
Boro had the ball in the net on seven minutes but Ryan Bennett's header was ruled out for a foul on Adam Barrett in the six yard box.
Soon afterwards, Dean Cox was appealing in vain for a spot kick at the other end when he brought down by the combined efforts of Gabriel Zakuani and James Wesolowski.
Adam Barrett marked his 500th game in some style on 18 minutes by collecting a yellow card for a foul on George Boyd. The free-kick was parried by the wall and then stopper Jamie Jones got a tangle with Craig Mackail-Smith. Heart in mouths time for home fans, before referee Iain Williamson booked Peterborough's main man.
The contest shaped up as an even and entertaining encounter with control of the midfield crucial. Orient were strong with Matt Spring running the show with a series of neat touches, pushing the ball around as required. Boro in contrast often looked to their front line with long balls up from the back.
Orient looked most vulnerable from set-plays. Boro dominated in the box from corners with a big ariel threat.
But shots on goal were rare until 10 ten minutes before the break, when Charlie Daniels and Harry Kane tested keeper Joe Lewis, who looked shaky in return. At the other end, Jones palmed over the crossbar Mackail-Smith's free kick, after Spring was booked for fouling Grant McCann.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here