Dean Cox put the hosts in front with a sixth-minute free kick but Jimmy Smith opened his account for Crawley by scoring the equaliser against his former club four minutes later.
Chris Dagnall (18) restored the home side's lead with a header and Crawley seldom threatened an equaliser in a scrappy second half before substitute David Mooney and Dagnall sealed the win for Orient with goals on 88 minutes and the fifth minute of stoppage time respectively.
John Gregory made four changes to the side that had lost 2-1 to Port Vale six days ago. With Crystal Palace unwilling to extend Lewis Price’s loan spell Brian Jensen returned in goal while Gwion Edwards was back after recovering from a hernia injury. There were also recalls for Conor Henderson and Matt Harrold.
Sonny Bradley (ankle), Josh Simpson (hamstring) and Lanre Oyebanjo (calf) were all injured while Izale McLeod completed his three-match ban. There were O’s starts for ex-Reds’ loanees Josh Wright and Shaun Batt.
With neither side in any sort of form a cagey encounter was anticipated but it was anything but with three goals in the first 18 minutes.
In the opening minute Batt’s low cross, after a neat exchange of passes with Cox, flashed across the face of goal with Dagnall inches away from applying a decisive touch.
Reds responded straight away and Shaun Miller’s cross was only cleared to Henderson, whose strike from 20 yards whistled inches wide.
Orient had clearly decided to attack Bobson Bawling at right-back at every opportunity and they went ahead on five minutes. Cox beat Bawling to find Dagnall and Dean Leacock was penalised for handball as he challenged the striker. COX took the free kick from the edge of the box and curled it expertly into the top left-hand corner, giving Jensen no chance.
But it took Reds just four minutes to equalise. Henderson’s cross was attacked by Harrold and, when his powerful header came back off the post SMITH, scrambled in the equaliser at the second attempt.
Henderson was involved again two minutes later when O’s keeper Adam Legzdins dropped his free kick but was perfectly positioned to block Edwards’ shot when the loose ball dropped to him.
Orient regained the lead on 18 minutes and again Cox was involved. He beat Bawling and teed up a cross which DAGNALL got a free header on to arrow it into the top right-hand corner.
After the flurry of early goals the game settled down a little. Smith tried an ambitious effort from 40 yards with Adam Legzdins off his line but his effort went wide.
Reds certainly carried a threat when they attacked but Orient also looked dangerous. Jobi McAnuff warmed Jensen’s hands when he cut inside and let fly then Scott Cuthbert headed wide from another fine free kick delivery by Cox.
Just before the break Harrold headed over from 12 yards before Miller joined Leacock in the referee’s notebook for kicking the ball away at the end of an entertaining first half.
Legzdins continued to look shaky in the Orient goal at the start of the second half although it was Jensen who made the first save after the break when he pushed substitute David Mooney’s drive around the post after Dagnall’s lay-off set up the opportunity.
Elliott Omozusi became the third Orient player to be booked for bringing down Smith and Harrold followed him into the book for a late foul on Shane Lowry.
Reds made a change on 67 minutes when Gavin Tomlin replaced Miller but at that stage Orient looked more likely to score the next goal with Wright volleying wide from just outside the box after a corner was only half cleared before going even closer with a drive from 20 yards after McAnuff’s shot was blocked.
Legzdins was substituted with 20 minutes to go because of injury and then Bawling was replaced by Lewis Young with Smith going to right back.
Jensen caused a moment of alarm when he dropped Mooney’s shot but no Orient player could take advantage before the keeper got down to make a decent save from Dagnall at the end of a home counter-attack.
Reds suffered another injury blow eight minutes from time when Dean Leacock limped off and Emmett O’Connor came on to make his League debut with Marvin Elliott dropping back into central defence.
And with three minutes of the game remaining Orient wrapped up the points. Mooney’s shot was superbly parried by Jensen then Elliott slid in to nick the ball off Dagnall’s toes but the Orient man recovered to tee up MOONEY who lashed the ball home from close range.
Then in stoppage time DAGNALL tucked home his second from close range after substitute Bradley Pritchard set up the opportunity with a low cross from the right.
Tomlin had a great chance to pull one back after good work by Henderson but he dragged his shot wide as Crawley failed to get a shot on target in the second half.
Reds now head into the final game of 2014 in the relegation zone with a massive home match to come against Colchester on Sunday.