Adrian Clifton netted early in the second half subjecting Orient to defeat in front of a 5,000 strong crowd at The Breyer Group Stadium.
This defeat leaves Orient third in the National League table, three points off leaders Solihull Moors, over whom the O’s have a game in-hand.
Head Coach Justin Edinburgh made two changes to the side who began the 1-1 draw with Hartlepool United last weekend.
Myles Judd signed a contract extension in midweek but dropped to the bench in favour of Sam Ling at right-back.
Meanwhile, Jay Simpson partnered Macauley Bonne in attack after re-joining the club for a second spell on a deal until the end of the season.
Electric Start
Orient got the game underway on an overcast afternoon in E10, kicking from right to left in their traditional red home strip.
They played with high intensity in the early stages as Charlie Lee headed over from Jobi McAnuff’s corner, before Sam Ling poked his effort wide at the far post.
With quarter of an hour played, the O’s looked confident and seemed to be playing with hunger, desire and belief.
Knock, Knock
Having carved out some fine openings, Orient continued to bang on the door of Maidenhead’s defence as Craig Clay’s strike was held by visiting goalkeeper Carl Pentney.
On the right, James Brophy linked nicely with Bonne who broke into the area only to be denied by the feet of Pentney once more.
At the other end, Clifton sliced the ball over the crossbar before Ryan Upward struck straight at O’s goalkeeper Dean Brill as the visitors searched for an opener.
Fully Booked
It was a battling affair with both teams showing their physicality throughout the half. Ayo Obileye received the first caution of the match after halting McAnuff’s bursting run.
Shortly after, Brill upended Clifton outside the area with the travelling faithful calling for a dismissal. After consulting his assistant, referee Simon Mather felt yellow was enough.
Just before half-time, Orient should have broken the deadlock. Simpson’s close-range effort was smothered by Pentney before a recovering defender blocked Clay’s rebound.
Stunned Silence
Maidenhead succeeded in catching the O’s off guard when they drew first blood seven minutes after the restart.
Clifton beat the offside trap, finding himself unmarked in the penalty area to guide the ball into the far corner and leave the Orient faithful on edge.
The O’s fans were vocal in trying to spur their side towards an equaliser. However, frustrations were beginning to grow as Clay was booked for a challenge on James Comley.
Fresh Formula
Time was against Orient who despite seeing plenty of the ball were struggling to conjure a moment of magic.
Edinburgh made three changes in seven minutes with Jordan Maguire-Drew, Dale Gorman and Matt Harrold entering the fray in a desperate attempt to salvage at least a point.
Instantly, Gorman fired into the grateful palms of Pentney before Harrold turned Clay’s fierce low cross agonisingly over the crossbar.
Rapid Response
After six minutes of stoppage time, the referee’s whistle secured a huge three points for Maidenhead, while Orient were left reeling at chances that went begging.
On reflection, the O’s can take comfort from the fact that fellow promotion hopefuls Solihull, AFC Fylde and Salford all slipped up but will be fuming that they failed to pounce.
Next week, Orient travel to holders Brackley Town in the FA Trophy quarter-finals where they will be desperate to make amends by taking a step closer to Wembley.
