Leeds had the better of the first half of Tuesday night's League One clash and midfielder Neil Kilkenny forced home keeper Jamie Jones to a 13th minute feet-first save, before they went ahead when Fabian Delph dispossessed Orient defender Charlie Daniels and fed winger Robert Snodgrass who shot just inside the far post on 19 minutes.
Orient midfield Jason Demetriou and striker Dean Morgan in turn went down in the box from token challenges and penalty appeals were waved away by referee Trevor Kettle.
Leeds went further ahead when Demetriou handled a shot from Luciano Becchio and was red-carded, allowing Snodgrass to convert a 58th minute penalty for his 10th goal of the season.
Orient promptly pulled goal back via a splendidly struck free-kick by midfielder Sean Thornton from a yard outside the penalty area on 66 minutes.
Jones kept Orient in contention with saves from midfielder Jonny Howson and Becchio and when Leeds keeper Casper Ankergren failed to hold Morgan's shot striker Simon Church scrambled in Orient's equaliser with six minutes left.
Leeds remain fifth and look set for the play-offs while Orient stay 15th and are now seven points above the drop zone.