A brace from Jay Simpson to open his account for the O's was enough for Orient to ease through to the third round of the Johnstone's Paint Trophy in a comfortable win at Victoria Park.
Orient came flying out of the blocks and Simpson got them off to the perfect start when he finished coolly after good work from Shaun Batt and the same man killed the game with 20 minutes to go when he smashed home a loose ball in the box.
The O's looked dangerous on the attack in front of almost 1,000 travelling fans who made plenty of noise throughout.
Kevin Nugent was in search of his first win in charge of the O's and changed the shape for the trip to Victoria Park as he opted for a 4-3-3 formation with Darius Henderson taking up the central role in a forward three flanked by Jay Simpson and Shaun Batt. For Batt it was a special night as his brother Damian lined up for the opponents.
Behind them, Romain Vincelot, Marvin Bartley and Bradley Pritchard made up the midfield three whilst it was a familiar looking back four to last season with Gary Woods continuing in goal.
There was a good number of travelling Orient fans and there were some familiar faces awaiting them in the Dagenham squad with Brian Saah starting and George Porter on the bench, both of course former O's men.
Orient came flying out of the blocks and Batt had already threatened in the early stages drawing a yellow card from Matt Partridge and with just five minutes gone he galloped through the Daggers' midfield and slipped in Simpson in the right channel who kept his calm to slot home his first Orient goal underneath Liam O'Brien.
The goal seemed to transform the former Arsenal man and with the confidence flowing just two minutes later he unleashed an effort from 30 yards that rattled against the woodwork with O'Brien well beaten.
It was perhaps the most attacking and dangerous that Orient have looked this season. The shape seemed to suit the forward three in particular with Batt and Simpson running well off of Henderson and looking a constant threat.
The only disappointing moment came with a quarter of the game gone when Mathieu Baudry hobbled off with a hamstring injury and Shane Lowry replaced him.
Simpson continued to be a thorn in the Dagenham side and with 25 minutes on the clock he wriggled down the left and fizzed a cross in that Henderson did well to head just a whisker wide.
Vincelot was the next to go down the left and cut back for Henderson who went close again three minutes later as Orient looked to get a second and kill the game.
The big man looked in the mood for a goal and he did well just after the half hour mark to collect Lowry's diagonal ball and curl a shot from distance narrowly wide of the target.
He went even closer still two minutes after when when Omozusi crossed from the left and Simpson glanced a header against the post and Henderson saw his follow up smothered well by O'Brien.
There was the odd scare though as the half wore on as first an Ashley Chambers free-kick caused chaos before being turned behind for a corner that Billy Bingham took which was glanced goalwards before being blocked on the line by Pritchard.
Orient saved one of their finest moves of the first half until last though when Henderson switched play brilliantly to Batt who collected it wide on the left and swung in a cross with his weaker foot that Simpson headed narrowly over the bar.
Nugent headed down the tunnel the happier of the two managers though his only regret would have been that his side weren't further in front.
Orient began in the second half in control albeit not to the same extent but were almost undone by a problem they have suffered before this season. After threatening from a corner, Orient lost possession and were almost pulled back by a Daggers' counter when Ade Youseff raced one on one with Clarke and got a yard on the O's skipper but blazed his effort over the bar.
With numbers thin on the ground, the O's were wishing for a second and the opportunity to rest some legs with a trip to Sheffield United on Saturday, yet the cup tie remained very much alive at 1-0.
With 25 minutes remaining, Lowry dipped a free-kick over the bar from distance as Dean Cox entered the fray to replace Batt who had been impressive throughout.
Cox had an instant impact when his low cross from the left was cleared only as far as the lurking Simpson who rifled home the loose ball for his second goal of the night.
The second goal effectively killed the tie as Pritchard appeared to limp off and was replaced by Harry Lee.
The O's managed the final stages well though to progress and it was the manner of the performance that would have pleased Nugent most as he collected his first win in charge of the O's.
Dag & Red: O'Brien, Batt, Doe, Saah, Bingham (Porter 75), Ogogo (Raymond 87) (C), Chambers, Doidge, Labadie, Partridge, Yusuff (Goldberg 67)
Subs: Cousins, Gayle,
Bookings: Partridge 3
Orient: Woods, Omozusi, Vincelot, Cuthbert, Baudry (Lowry 24), Batt (Cox 68), Clarke (C), Pritchard (Lee 77), Bartley, Henderson, Simpson
Subs: Grainger, Kashket
Goals: Simpson 5, 69
Att: 2,318 (982)
Ref: J Linington