Few would have tipped the O's to salvage anything from an exciting encounter, after two goals from Robert Snodgrass put Leeds 2-0 ahead and a red card for Jason Demetriou saw the home side reduced to ten men early in the second half.
However, late goals from Sean Thornton and Simon Church saw Orient grab a deserved point.
It was the away side that started the brighter with Neil Kilkenny going close in the 13th minute, before good work by Fabian Delph enabled Snodgrass to run through and slot the ball past Jamie Jones in the 19th minute.
Leeds almost doubled their lead nine minutes later when Ben Parker shot just wide with a delicate chip from the edge of the box.
The O's took their time to impose themselves and their only real chance in the first half fell to midfielder Jimmy Smith, whose spectacular volley flew inches over the bar in the 34th minute.
It was the second half that provided the excitement though. Firstly, on 58 minutes, O's midfielder Demetriou was dismissed for handling on the line, before Snodgrass hammered home the resulting penalty.
The O's looked dead and buried but got themselves back in the game just seven minutes later, when Thornton fired in a free-kick from the edge of the box.
Three minutes later a wonderful double save from Jones denied Snodgrass a hat-trick, but it was the spirited home side who continued to cause problems and on 84 minutes they got their reward.
John Melligan's cross was turned back across goal by Dean Morgan only for Leeds keeper Casper Ankergren to fumble gifting Church a chance to pounce and complete the dramatic comeback.