DAVID MOONEY secured Orient's place in the area final of the Johnstone's Paint Trophy in the most dramatic of circumstances on Tuesday night.
A man light after Anthony Griffith was dismissed 14 minutes from the end, Mooney popped up to head home in the final minute and defeat Yeovil Town.
Mooney's hot streak continued as he made it 10 goals in 12 games, but few before had matched the importance as this one with the O's now just one round away from Wembley.
It was the hosts who had the first shot in anger when space opened up for Lloyd James to try his luck from 25 yards, but the Welshman dragged his right footed effort wide of the mark and Marek Stech was untroubled in the away goal.
Chances were few and far between in the early stages, although Jamie Jones had to spring down to his left to touch Dominic Blizzard's volley around the post after a free kick launched high into the O's box dropped for the Yeovil midfielder.
The game was mainly being played out in midfield and it wasn't until the 37th minute that another half chance arrived as Gavin Williams crossed from the right for the visitors and Jamie McAllister's downward header was easily saved by Jones.
Three minutes later Dean Cox delivered a corner at the other end and Ben Chorley headed towards goal, but Stech managed to save with David Mooney lurking in front of him.
Moses Odubajo tried to force the issue for the O's at the start of the second period, drawing a parry from Stech on 54 minutes with a shot from outside the box.
But the O's were then dealt a blow when Kevin Lisbie was forced off with an injury and Matt Dolan almost increased their woe when he spotted Jones off his line and went for goal from 45 yards but, much to the home side's relief, the ball dropped wide of the mark.
With 69 minutes on the clock, the O's created a decent chance when Dean Cox knocked the ball beyond left back Daniel Burn on half way, cut in off the flank and swept the ball across to Moses Odubajo, who cut back onto his right foot and shot for goal only for Stech to touch over the top.
Orient's challenge then faced a major threat as Grifffith picked up two bookings - the first for a foul on Williams, the second for kicking the ball away - in the space of three minutes.
It meant the home side had to play out the final 14 minutes a man light, but Yeovil didn't make the most of it and the O's punished them right at the death.
Mooney has loved the cup competitions this term, notching six of his nine goals up to this game in the FA Cup and Johnstone's Paint Trophy and he added a seventh in fine style.
Scott Cuthbert delivered the cross from the right with his weaker left foot and Mooney nodded down and across Stech to spark delirious scenes at Brisbane Road.
Six minutes of stoppage time were signalled, but it was the O's who nearly sealed it when Lee Cook broke away and sent a shot crashing against the bar.
Glovers keeper Stech went forward for a free kick and a corner as the Glovers desperately searched for a leveller, but when Jones saved from Daniel Burn's header it was all over and the O's were just one round from Wembley.
Leyton Orient: Jones; Cuthbert, Baudry, Chorley, Saywer (Cook 74); Odubajo, Griffith, James, Cox; Mooney, Lisbie (Symes 61)
Subs: McSweeney, Smith, Allsop (GK)
Goal: Mooney 90
Booked: Griffith, Odubajo, Mooney
Sent off: Griffith
Yeovil: Stech; Ayling, Webster, Hinds, Burn; Williams (Ralph 78), Blizzard, Upson (Dolan 49), McAllister; Foley (Dawson 74), Hayter
Subs: Reid, Stewart (GK)
Referee: Carl Berry
Attendance: 2,755 (810 away)