Bramall Lane's biggest crowd of the season saw skipper Billy Sharp guide United to another three points.
A crowd of 25,821 saw gutsy Oldham undone by two second half strikes from Sharp, who took his tally for the season to 16.
For the third consecutive game, boss Wilder named an unchanged starting XI. There were changes on the bench where Scougall and Brooks replaced Hussey and Whiteman. The visiting team included former Blades favourite Flynn, who received a warm welcome ahead of kick-off.
The first three minutes were mainly played out in the Oldham half, resulting in the game's first corner but Ebanks-Landell was felled as the visitors cleared. The first chances dropped to the away side. Osei shot at Moore and then, on eight minutes, a counter-attack following a counter-attack saw Flynn's 20-yard shot acrobatically pushed over the crossbar by Moore. A little later Flynn was the first to be booked, for a late challenge on Freeman.
United had a spell of pressure without creating a chance, although O'Connell joining in an attack on 17 minutes caused a nervous moment for the visiting defence. On 28 minutes a deep Done cross was perfect for Sharp but his header deflected off Clarke and dribbled wide.
The Blades then went close three times in four minutes and Done was involved in the build-up for each. From a break, Duffy's cross was headed into the dangerous area by Lafferty but the ball across the box evaded both Sharp and Done. Then, Duffy's free-kick was on target but saved by Ripley, who was also ideally placed to collect O'Connell's back post header from a Coutts corner.
Basham moved into midfield as half-time approached and the final chance of the half saw McKay half volley over for the visitors.
Following a slow start to the second half, Clarke replaced Done and the bumper crowd did their best to raise the temperature, despite a lack of opportunities. Duffy was crowded out as he prepared to shoot and Fleck pulled a free-kick back for O'Connell but he was off target.
Oldham's first opportunity of the half, on 66 minutes, was the result of mistake between Basham and Ebanks-Landell, but O'Connell blocked from McKay. Law also curled a free-kick over, whilst between these Sharp shot over on the turn from a Freeman cross.
United went close again from a Coutts cross and Clarke header, which beat goalkeeper Ripley but Wilson sliced his clearance just wide of goal - although the opening goal was just around the corner.
The ever-dangerous Duffy clipped a ball over the defence and SHARP positioned his body behind the ball, keeping his marker away, before half-volleying a shot that was too quick and accurate for Ripley.
Oldham went close to a close to a leveller five minutes later but Moore palmed away a Ladapo shot from the edge of the box, but United were still on top.
Freeman's shot was blocked by Peter Clarke after good work from Leon Clarke and a Duffy shot was pushed away by Ripley. There was also a penalty appeal when Basham went down under Ladapo's challenge.
The Blades, though, had to wait until 88 minutes before registering a second. Again Duffy provided the assist and following Clarke's challenge on Ripley, the ball broke for SHARP to drill home.
Five minutes of injury time saw United barely tested the only chance of the extra period saw Clarke fire over a Basham cross before the final whistle signalled three more welcome points.
Blades: Moore, Fleck, O'Connell, Basham, Sharp, Done (Clarke 54), Coutts (Wright 89), Freeman, Ebanks-Landell, Duffy (Scougall 90), Lafferty.
Unused: Lavery, Ramsdale, Brown, Brooks.
Oldham: Ripley, Law, Wilson, Flynn, McKay, Dummigan, Osei (Ladapo 73), Clarke, McLaughlin, Green (Winchester 87), Dunne (Croft 80).
Unused: Burgess, Banks, Kettings, Edmundson.