Two goals in the space of four second half minutes saw Orient make it back-to-back victories as they secured a vital three points at Walsall.
After a goalless first half, Ryan Hedges broke the deadlock on 65 minutes before he turned provider to set up Chris Dagnall for his 10th of the season.
Boss Fabio Liverani made one change from the team which beat Oldham Athletic 3-0 with new loan signing Luke O’Neill coming in for his debut, with Gary Sawyer making way.
There was a return to the bench for Scott Cuthbert, who had been out with an ankle injury.
Orient started brightly and Jobi McAnuff’s cross was deflected behind for an early corner, before Andy Taylor up the other end saw a free-kick well held by O’s goalkeeper Alex Cisak.
Another corner came the O’s way, but chances were few and far between.
Cisak did well to block a Jordy Hiwula cross behind for a corner, before McAnuff was involved once more in another attack for the visitors.
His ball in found Dagnall and his attempts to fashion some space in the box was unsuccessful, but the ball fell to Josh Wright and his effort was blocked.
McAnuff was then inches away from getting on the end of a through ball, however, Saddlers goalkeeper Richard O’Donnell was out to block at his feet as Orient dominated the chances.
The best continued to come the way of the visitors as Dagnall flashed an effort wide before Mooney chested down a throw-in and scooped a shot just off target.
Some good build-up play from Liverani’s side saw McAnuff play in Dossena and his ball into the box was just glanced wide by the head of Dagnall.
Neither side made changes at the break, and Dagnall opened the half with the first effort – blazing over from an acute angle.
But the visitors would take the lead on 56 minutes when Walsall failed to clear a free-kick and Josh Wright played in Hedges who fired across goal and past O’Donnell.
And it got even better for the visitors just three minutes later when Hedges turned provider as his threaded ball through found Dagnall who rifled an effort into the back of the net to double the O’s lead.
Hedges received rapturous applause when being replaced by Dean Cox with 15 minutes left, and Orient looked relatively comfortable.
Substitute Simpson and Mooney linked up well, with the former just seeing an effort squirm wide of the target.
Walsall failed to threaten the visitors too much, and Orient made it back-to-back wins and clean sheets as the O’s head into Tuesday’s home match with Bristol City.
Walsall: O’Donnell, Purkiss, Taylor, O’Connor, A Chambers, Bradshaw (Bakayoko 81), Sawyers, Cain (Flanagan 65), J Chambers, Cook (Grimes 74), Hiwula.
Substitutes: Downing, Baxendale, Bakayoko, Murphy, MacGilvray.
Bookings: Purkiss 55
ORIENT: Cisak, Dossena Baudry, Lowry (Cuthbert 90), O’Neill, McAnuff, Wright, Vincelot (c), Hedges (Cox 75), Dagnall (Simpson 83), Mooney.
GOALS: Hedges 56' Dagnall 59'
Substitutes: Sawyer, Clarke, Bartley, Woods.
Attendance: 5,239 (451)