With both teams campaigns faltering of late it was Rochdale who suffered the blues on a freezing winters afternoon mugged by Orient's fierce determination which sent the home side sliding down the table.
Rochdale have only themselves to blame conceding two of Orient's goals through inertia from set pieces. The first after 9 minutes when Matthew Lockwood swiftly took a free kick lobbing the ball into the home penalty area for Gary Alexander to meet perfectly with his head while the home defence was still organising itself.
Rochdale leveled matters through a blockbuster shot by Alan Goodall on 22 minutes only for Shaun Tudor to retake the lead for the visitors 12 minutes later however Tudor's over exuberance brought him his first yellow card for whipping off his shirt in front of the visitors stand.
Two minutes before half time Tudor was given his marching orders for a crunching tackle on Alan Goodall.
Immediately after the break Orient further tightened their control on the game with another softly given away goal by the home side.
Lee Steele did all the hard work to beat three Rochdale defenders and give Alexander his second goal.
A never say die Rochdale kept battling and looked as if they were going to get back into the game through Blair Sturrock and then saw a Ricky Lambert equaliser disallowed.
But Orient despite being a man short kept their nerve and secured their first win at Spotland in six years with a fourth goal from Joe Mackie.