Moses Odubajo put Orient ahead in the 14th minute but two goals before half-time from Gary Alexander and Andy Drury put them on the back foot, with Nicky Adams's 76th-minute strike wrapping up the win for Crawley, despite Marvin Bartley's late score.
Wolves missed the chance to overhaul the O's at the top of the pile as they drew level on points after a 3-3 draw away at Rotherham.
Danny Batth's headed opener for Wolves was cancelled out 60 seconds later by Nouha Dicko in the 11th minute, with Kieran Agard putting Rotherham ahead at the break.
Dicko scored again early in the second-half and the Millers looked to be cruising until Bakary Sako pulled one back from the penalty spot and James Henry netted the equaliser in the 64th minute.
Brentford lie third thanks to their 3-0 win at Preston.
Adam Forshaw scored the opener from the penalty spot with Marcello Trotta and Sam Saunders making sure of the points, as Joe Garner missed a second-half penalty for Preston.
Swindon moved just outside of the play-off places as they came from behind to claim a 2-1 win over Coventry.
Leon Clarke headed the opener for Coventry in the 51st minute, but goals by Yaser Kasim and Miles Storey saw the home side claim the win.
MK Dons were 3-0 winners at home to Port Vale.
Stephen Gleeson, Ben Reeves and Patrick Bamford all scored for the Dons in the first half.
Elsewhere, Walsall beat Carlisle 2-0 thanks to goals from Romaine Sawyers and Milan Lalkovic, with Courtney Meppen-Walter dismissed for serious foul play for the visitors with three minutes remaining.
First-half goals from Kgosi Ntlhe and Britt Assombalonga saw Peterborough claim a 2-1 win over Bradford, with Andy Gray's 76th-minute score only proving to be a small consolation.
Ellis Plummer's eighth-minute own goal and Jabo Ibehre's close range score saw Colchester beat Oldham 2-0 while Stevenage drew 0-0 against Sheffield United.
Notts County salvaged a last-gasp 1-1 draw against Bristol City when Alan Sheehan's 89th-minute penalty cancelled out Sam Baldock's first-half spot-kick while Crewe also drew 1-1 against Shrewsbury, Jon Taylor cancelling out Tom Hitchcock's headed opener for the home side.