Tom James's superb strike and a Lawrence Vigouroux clean sheet on his 100th consecutive league start saw Leyton Orient to a second successive League Two victory.
O's went close after just three minutes when debutant Charlie Kelman teed up Ruel Sotiriou, who blazed over from 12 yards.
The home side had a good chance of their own on 20 minutes when a flowing passing move found James Tilley at the far post, but he fired wide with the goal at his mercy.
Kelman's backheeled pass then found George Moncur, but George Francomb blocked the attempted cross and Sotiriou had a shot deflected behind for a corner moments later.
Theo Archibald's half volley from the edge of the box was straight at Corey Addai on 27 minutes and he fired a free-kick into the wall after Kelman was fouled by Dion Conroy just outside the box.
James, after his wonder strike in the 2-0 home win over Grimsby Town a week earlier, then advanced upfield late in the half but sent his effort wide of the target.
And an Archibald cross created confusion in the home defence during stoppage time, almost evading Addai and drifting behind for a goal kick.
The visitors took the lead six minutes after the restart, though, as a corner from the left was cleared and James found the net with a right-footed half volley from outside the area.
And Sotiriou made way for Paul Smyth moments later as Richie Wellens made his first change of the afternoon.
Omar Beckles headed just over from Archibald's cross as the travelling O's supporters found their voice behind the goal, but Vigouroux had to make a good claim for the ball at the other end when under pressure from Tilley's cross.
Kelman made way for Harry Smith on 63 minutes, after a good first outing for the club, and Smyth pulled a shot wide of the target after winning possession from Conroy two minutes later.
Darren Pratley was next to try his luck after showing superb control, arrowing a shot goalwards but seeing it fly just over the crossbar.
But Crawley then countered well through Liverpool loanee James Balagizi, only for him to overhit his pass for Ashley Nadesan to let O's off the hook.
And Dan Happe cleared Travis Johnson's cross as the visitors continued to come under pressure with a quarter of an hour remaining.
Shad Ogie came on for Archibald with 11 minutes remaining to bolster the O's defence and Addai claimed the ball at the second attempt, having dropped it under pressure, before Rob Hunt could profit.
Vigouroux claimed a cross from Kwesi Appiah at the other end, before six minutes of stoppage time were signalled and Smyth went down in the box, then fired into the side netting after penalty appeals were turned down.
Appiah's shot was saved by Vigouroux as O's held on for the points ahed of their trip to Forest Green Rovers in the EFL Cup on Tuesday.
Leyton Orient: Vigouroux, James, Happe, Clay, Sotiriou (Smyth 53), Archibald (Ogie 79), Moncur, Pratley, Beckles, Kelman (Smith 63), Hunt. Unused subs: Sargeant, Thompson, Georgiou, Sweeney.
Attendance: 3,851 (including 815 Orient fans).
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