A minute's silence was observed before kick-off in memory of Princess Margaret, who died this morning after a stroke.
The weather was foul for Albion's successive home wins against Cardiff and Tranmere and conditions were difficult once again.
Kuipers, seeking a third clean sheet in a row since his return from injury, had the elements against him but another strong contingent of Albion fans literally behind him for the opening 45 minutes.
Appleby, Oldham's on-loan Barnsley midfielder, required prolonged treatment after an accidential collision with Hart.
When Appleby rejoined the action he immediately delivered a cross from the left just out of reach of the head of Oldham's topscorer Eyres.
The Seagulls were threatened next by a four-man move involving Oldham's 37-year-old duo of Eyres and skipper Sheridan.
Eyres' lay-back from Armstrong's cross into the box was left by Murray for Sheridan to blaze over from 20 yards.
Oatway, subsituted at half time against Tranmere as part of a tactical change, showed typical tenacity.
He lost possession midway inside the Oldham half but scurried back to retrieve the situation halfway inside Albion territory, winning a free-kick off Reeves in the process.
The pitch was surprisingly firm and Kuipers misjudged the bounce of a wind-assisted ball down the right by Armstrong.
The big Dutchman miscued for a corner after advancing outside his area.
Oatway threw himself into a block from a shot by former Southampton midfielder Murray as Oldham hunted for a breakthrough.
Pethick continued the role of emergency goal kicker which he adopted in the second half against Tranmere after Kuipers suffered a recurrence of thigh trouble.
The first sign of Albion as an attacking force came midway through the half when Cullip, making his 100th League appearance for the club, headed over from a Watson free-kick.
A free-kick by Sheridan, only half cleared by the Albion defence, was volleyed way wide of the target by Oldham's giant French defender Baudet.
Webb collected a costly caution in the 28th minute for a dive ten yards inside the Oldham half when he felt he deserved a free-kick.
The young striker's third yellow card in five games for the Seagulls follows seven for his former club Southend.
It means Webb now faces an automatic two-match ban, ruling him out of the home game against Wrexham on February 23 and the trip to Bournemouth three days late.
Worse followed for Albion as they fell behind two minutes later.
Appleby met a corner from Eyres with a right foot volley from just inside the box which sped low and hard past Kuipers into the far corner.
Appleby's second goal in four outings rather upset Albion's game plan. Up to that point they had coped pretty comfortably.
The deficit nearly doubled on 34 minutes when Corazzin looped a long range header narrowly wide from a cross by Murray.
Albion missed a great chance to restore parity on 40 minutes through Rogers.
The captain, who opened the scoring against Oldham at Withdean, was put clear by Pethick's pass but dragged an angled shot wide from ten yards.
Oldham were forced into a midfield change moments later, club captain Duxbury replacing the injured Sheridan.
Albion had their first effort on target a minute from the break, Carpenter's free-kick from 30 yards bouncing comfortably into the arms of Rachubka.
Oldham deserved their half time advantage, but Rogers might easily have hauled albion level and the cause was by no means lost with the wind in their favour in the second period.
Half-time: Oldham 1, Albion 0.
Early into the restart Carpenter drove wide from 25 yards after Brooker and Watson combined to feed him.
Substitute Duxbury was booked on 49 minutes for a challenge on Hart - Oldham's 17th infringement proving they were in no mood to take prisoners.
Webb went down inside the Oldham area in an off-the-ball incident which appeared to involve Baudet.
It was not spotted by referee Chris Foy or his assistant and Webb was soon back up on his feet as play continued with an Albion throw-in.
Albion reverted to an orthodox 4-4-2 from the 4-5-1 formation which began the game, with Hart on the left and Brooker playing alongside Webb.
Tempers frayed when Webb won Albion a free-kick, with Oldham protesting that he had dived again.
Before it could be taken Taylor brought on Zamora to replace Webb who was in danger of being sent off.
Zamora made an instant impact. His first touch within two minutes of coming on was a header which crashed against the crossbar from a diagonal cross by Watson.
Zamora then wrong-footed the Oldham defence with a dummy which released Brooker to shoot straight at Rachubka.
The sides made simultaneous substitutions, Melton replacing Rogers in the middle of the Park for Albion and Smart coming on upfront for Oldham at the expense of Reeves.
Hart was left with his hands on his head in frustration when, set up by Zamora, his fierce 20 yarder was inadvertently deflected away from goal by Brooker.
Lewis was introduced for his debut with 16 minutes left in place of Oatway, a former colleague with Middlesex Boys.
Moments later Hart exchanged passes with Zamora, only for Rachubka to make a fine smothering stop at the expense of a corner.
Eyres sealed the Seagulls' fate on 81 minutes with an unstoppable free-kick into the top corner from 18-yards.
Albion's misery was completed on 84 minutes when Zamora received an automatic red card for kicking out at Armstrong off the ball.
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