Nick Blackman's fifth goal of the campaign - a curling left-footer - was enough for the Blades to record a second away win of the week.
The striker struck just before the hour to continue the unbeaten start to the campaign.
United's defence, already without Neill Collins, lost goalkeeper Mark Howard on 11 minutes through injury but 18-year-old George Long looked assured as the Blades recorded a clean sheet against a team who had lost just once in their last six games.
Boss Wilson was forced into a change... Williams drafted into the starting line-up in place of Collins, who was suffering with a toe problem. It meant a revamped back four with Hill moving inside to partner Maguire, with Williams slotting into a familar left-back position.
The Blades - playing in the white, second change shirts - were the first on the offensive, a ricochet almost put Flynn in and the space opened up for McMahon to have a pop at goal, unforfunately it was on his unfavoured left foot.
With 11 minutes gone Wilson was forced into a change when Howard pulled up, holding his thigh after taking a goal-kick.
After treatment it was clear he could not carry on and was stretchered off, his place taken by Long. Hill quickly protected the teenage goalkeeper by producing a timely tackle as Cox looked to wriggle free.
Two more McMahon shots failed to open the scoring, whilst the right-back provided the cross for Blackman to shoot over on 16 minutes. The chances tailed off as the half wore on, although Smith went close for the home side and from the resulting corner, Chorley's header was kicked away by Kitson.
Just before the break, McDonald slipped when in a good position following a Flynn pass and after a break down the right, Kitson pulled a shot wide. There was also time, before the half-time whistle, for Gallagher to fire wide from 25 yards.
United started the second half well, passes totalling more than 20 ended with Flynn winning a corner, but twice Blackman was pulled up for handball and Gallagher put a little too much on two crosses.
But just before the hour, however, the endeavours of the visitors were rewarded. Flynn and McMahon were both involved on the right ahead of Kitson's pass inside to BLACKMAN, who moved the ball onto his favoured left boot before curling perfectly into the top corner.
In response, Lisbie and Cook were involved before Griffith sliced wide, but the Blades were soon back on the attack and a great move on 67 minutes almost yielded a second. McDonald and Flynn combined down the right and the latter's drag back was ideal for the onrushing Doyle, who agonisingly saw his shot blocked by both legs of goalkeeper Allsop.
On 70 minutes Long made a tremendous reaction save from Lisbie's header, the goalkeeper unaware of a raised offside flag, and Cook fired over a free-kick. The Blades protected the slender lead well by keeping hold of possession, whilst Wilson made a double swap up top in the final ten minutes - Cresswell and Porter replacing Blackman and Kitson.
Five additional minutes were signalled by the fourth official but the only action of note was a Cresswell shot, which was gathered by Allsop before the final whistle was blown.
Orient: Allsop, McSweeney, Sawyer, Chorley, Cox, Griffith, Lisbie (Brunt 78), Smith (Symes 45), Clarke, Cook, Rowlands (James 82).
Unused: Baudry, Laird, Odubajo, Mooney.
Blades: Howard (Long 11), Maguire, Hill, Flynn, Doyle, Blackman (Cresswell 84), McDonald, Kitson (Porter 84), Gallagher, McMahon, Williams.
Unused: Westlake, Miller, McAllister, McFadzean.