Dan Kemp struck the bar in either half, and in truth Orient should have been out of sight – but Grimsby changes saw them threaten The O’s late on.
McAnuff made three changes to his team – as Widdowson, Turley and Clay started, with Dan Happe amongst those dropping to the bench.
It didn’t take long for him to join the action though, after a nasty head injury forced centre-back Adam Thompson off of the pitch after a lengthy delay.
James Brophy, playing in a wide attacking position, looked to be Orient’s main threat early on, and found lots of space out wide.
After fifteen minutes, he could have opened the scoring, but saw his low drilled effort blocked by a Mariner’s defender, and cleared.
The pressure mounted for Orient with successive corners, and soon after the breakthrough came.
A short corner between Freeman and Kemp caught Grimsby unawares, and after Kemp had fizzed a cross into the area – Happe reacted fasted, and was able to convert from close range.
This set Orient going, and on the stroke of half-time, the lead should have been doubled.
After Brophy was once again unleashed on the left hand side, his cutback to the advancing Dan Kemp was a clever one – and Kemp took aim.
His shot was a powerful one and had the keeper beaten, but his effort powered back off of the crossbar, and kept Grimsby in the game.
Orient came out of the traps quickly, and after a penalty shout for handball was turned down, again came close.
Once more, James Brophy’s excellent work found Dan Kemp unmarked in the box – but it was de ja vu for the diminutive winger – who’s deft touch goalwards bounced once again off of the bar.
Grimsby soon responded with the double change of John-Lewis and Hanson, and pushed into a 442 formation – which saw them ramp up the intensity.
John-Lewis was straight into the action, and after striking a half-volley wide, had a great chance to level.
The forward was found in plenty of space, and with a shot from outside of the area struck the left hand post – with Orient breathing a sigh of relief.
Orient had a couple of late chances, substitute Tristan Abrahams unable to get his low strike on target – but some great defending from Jamie Turley and Dan Happe at the back saw The O’s see out their first away win since November.
Grimsby Town: Eastwood, Bunney, Waterfall ©, Menayese, Hewitt, Morais, Rose (Hanson 66’), El Mizouni, Matete, Adams (Lamy 73’), Payne (John-Lewis 66’)
Subs unusec: McKeown, Hendrie, Habergham, Coke.
Leyton Orient: Vigouroux, Widdowson, Cisse, Clay © (Kyprianou 78’), Kemp, Brophy, Akinola, Freeman, Thompson (Happe 5’), Johnson (Abrahams 86’).
Subs unused: Sargeant, Ling, Wilkinson, Dayton.
Goals: Happe 20’