ORIENT held Leeds at Elland Road for almost the whole game tonight and were only undone by a rare lapse from Ben Chorley with only two minutes to go.
He mis-controlled one of the long balls which an under-par Leeds had lumped up field all night and forced skipper Stephen Purches into conceding a throw-in.
From that, substitute Max Gradel wound his way into the area and fired high into the net past Jamie Jones.
It was an 89th minute hammer blow for the O's players who sunk to the ground. They deserved so much more from this game which saw them produce one of their strongest performances this season.
The visitors outplayed the League One table toppers all through the first half, and then in the second period they defended well against a barrage of attacks by promotion chasing Leeds.
Andros Townsend shredded his markers all the way through this contest, while at the back Tamika Mkandawire was imperious against the division's most dangerous striker, Jaermaine Beckford.
Now Orient can consider it a pity there is no game on Saturday, because the display they produced in Yorkshire tonight would beat almost any team in League One.
Right at the start, the O's had the ball in the net in the sixth minute, when Andros Townsend thumped Sean Thornton's quickly taken free kick high into the far corner, after Townsend had been fouled by Leigh Bromby.
But the referee inexplicably called back the ball for the kick to be retaken.
Then on 13 minutes, Sean Thornton had a great chance dead centre in the middle of the area when he met Jimmy Smith's lay-off from Charlie Daniels' pin-point cross.
Patrick Kisnorbo's last ditch tackle nudged his effort wide.
The visitors had the best of the early chances, as Geraint Williams decision to flood the midfield with five players unsettled the hosts. They struggled to supply Beckford in the opening 15 minutes.
Townsend proved himself a handful and always drew fouls by Leigh Bromby. One passing move he orchestrated in the middle of the park during the first half was pure samba stuff, as it sliced through Leeds.
By contrast, Leeds spent the first part of the game lumping high balls in the general direction of Beckford, and they were ably dealt with by Mkandawire and Ben Chorley.
Beckford was in Mkandawire's pocket for extended spells. By the end of the first half he had moved over to the left to escape the Mali man and try his luck against Stephen Purches.
Mkandawire was masterful against League One's hottest hitman all through the game.
Frustrated home fans were on their players back half way through the first period when all they had seen was Neil Kilkenny blaze the ball into row Z.
Adam Chambers was a force at the heart of midfield but the officials penalised so many of his firm challenges on the home players who collapsed under pressure from him.
On 30 minutes, McGleish drew a save from keeper Casper Ankergren after Chambers had nutmegged left-back Andrew Hughes.
Leeds broke immediately up the other end with a long ball which Beckford laid off to Vokes. His effort drew more derision from the home fans.
Leeds were inept at times in the first half as passes went astray and players seemed to singing from separate hymn sheets.
On 35 minutes, Townsend pounced on a loose ball in midfield, and laid it off to Daniels. It took a clattering challenge from Kisnorbo to deny McGleish from 12 yards out.
Jamie Jones was not tested by a shot until the 42nd minute when jonathan Howson snuck in from the side and fired a shot straight at Jones.
With half-time looming, Orient started to hang back and let the Leeds midfield into the game.
JJ Melligan supplied some entertainment during the break when his well-aimed punt hit Leeds' bizarre white leopard-esque mascot smack in the side of its oversized marsh-mellow shaped head.
Into the second half and Leeds started like the proverbial whippet released out of a bag.
After going missing in the first half thanks to the visitors excellent pressing, Leeds danger-man Robert Snodgrass fired his first shot of the contest wide into the North End inside the first minute.
Orient did not pick up the loose ball like they had the first half, and Leeds came on strong as a result. They started to dominate the midfield and reaped the rewards in terms of pressure on Orient's area.
At times during the second half there were ten Orient shirts behind behind the ball. Max Gradel caused problems for Daniels after he came on on 62 minutes.
But the visitors continued to play some of their finest football of the season and be a threat, even with Townsend being harried and pressed more by Leeds.
On 53 minutes, Townsend flashed a low ball across Leeds goal-mouth from a visionary pass by McGleish on the fringe.
Gradel's looping effort on 71 minutes found the roof of the net in Leeds' best move of the match after Chambers was dispossessed by Snodgrass on the edge of the box.
Into the final 15 minutes and Mkandawire made an amazing tackle in the heart of the area to nick the ball from Beckford's feet as the striker wound up his shot.
On 83 minutes, Gradel's mis-hit cross had Jones reaching for the save for the first time in the match.
Gradel netted for Leeds on 88 minutes with a shot high into the net from 12 yards out from a needless throw-in which Chorley had forced Purches to concede after he mis-controlled a long ball.
It proved fatal, but Orient have so much to be glad about from this performance.
Jones, Purches, Chorley, Mkandawire, Chambers, McGleish (Scowcroft 59), Thornton, Daniels, Summerfield, Smith, Townsend.
Subs: Morris, Ashworth, Melligan, Demetriou, Jarvis, Cave-Brown, Scowcroft.
Attendance: 19,744
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