Darlington will have to wait another season to end their 34 year run without a win at Brisbane Road - assuming both sides are in the same division next season.
While Orient collected the three points to keep them in sight of the automatic promotion places, only the super-optimists believe that Quakers can still squeeze into the play-offs. They are now in 17th position, three wins off the play-off places, and have lost six out of their last seven league games.
However, they could count themselves unlucky not to go home with a point from Brisbane Road, after a dogged defensive display frustrated a home side that had previously dropped points just twice at home this season.
The setting wasn't one for the purist. A hard and bumpy pitch which was well sanded in places, meant from Darlington's point of view it was a case of safety first.
They produced what was probably one of their best defensive performances of the season. They restricted Orient to just a handful of chances, and it was clear that something special was needed to break through.
Unfortunately Orient midfielder Scott Houghton answered that question eight minutes from the end to sentence Quakers to their fourth successive away defeat. They can't afford many more if they're to make an impact on the play-off places - indeed some pessimists think that there might still be a battle against relegation - but surely another winning run similar to the one at the start of the season has to come along soon if only to lift the spirits of the fans.
Darlington manager Gary Bennett brought back Stuart Elliott into the right side of midfield, and taking the pitch into consideration, pushed Gary Himsworth into left midfield in place of Richard Hodgson.
The effect was that Quakers looked much more solid - at least, until that late goal - although some of their attacking flair was sacrificed with a defensive looking midfield.
"I thought the workrate of the lads was tremendous," said Bennett.
"They dug in, worked hard for each other and were solid. I don't think that Orient hurt us, apart from the goal.
"The pitch stopped us playing our normal passing game, but we did everything right and frustrated Orient.
"I was, though, a little disappointed with their goal. We didn't deal with the long throw into our box first time, but it was a great strike, one of those which could have gone anywhere.
"That's the way our luck has been going."
Quakers relied on swift breaks for their chances, and Bennett added: "When you play away from home, you expect to have two or three chances. Instead, we had four or five chances in the second half, when the ball was going across their box. I thought the header near the end was going in."
Quakers were in control of the game early on, and apart from a good tackle by Neil Aspin on Ahmet Brkovic, didn't have any problems.
They nearly took the lead after 13 minutes when Andy Collett caught the Orient defence flatfooted with a long clearance which Kevin Kyle latched on to, but under a lot of pressure, he lobbed the ball wide.
Quakers often found themselves in good positions down the left, but too often they wasted the ball.
So composed and tenacious were Quakers, that Orient's first real chance didn't arrive until the 24th minute, when Brkovic crossed from the right for the unmarked Houghton to volley high over the bar.
Orient didn't do much else for the rest of the first half, apart from a header from KK Opara which went wide. Quakers, meanwhile, were content to soak up the pressure and wait for the break, with Martin Gray always a driving force.
Orient nearly snatched the lead after 50 minutes when Andy Collett failed to hold a curling shot from Houghton, but the assistant's flag prevented Brkovic scoring from the loose ball.
Kyle had his second clear chance of the game after 57 minutes when Elliott found him bursting through, but after he shrugged off a defender he sidefooted straight at Ashley Bayes in the Orient goal.
Bennett then had to replace Gary Himsworth - who came off second best against an advertising hoarding - with new signing David McMahon, and Glenn Naylor dropped back into midfield.
And McMahon was nearly involved in a Darlington winner, when his left wing cross was just too far for Kyle, but when the ball came back into the middle, Paul Heckingbottom headed just wide.
But just as everybody was thinking of a clean sheet, Houghton grabbed the winner with a lovely goal. The Darlington defence failed to clear a long throw from the right, and the ball dropped for the unattended Houghton to fire past the helpless Collett from just outside the area.
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