Neil Harris converted a controversial 56th-minute penalty as Millwall recorded their first away win of 2010 at struggling Oldham Athletic.
Latics skipper Sean Gregan seemed to have escaped punishment after sending Steve Morison sprawling in the box, then raising his hands and appearing to grab the striker by the neck as he got up off the deck.
Although play had continued and with Oldham on the attack, referee Andy Haines spotted his linesman furiously flagging and following a lengthy consultation, booked Gregan and pointed to the spot.
Harris, making his first start in 14 games following injury, kept his cool to send a low shot into the bottom left corner with a precision finish that gave keeper Dean Brill no chance.
Up until that point, Oldham had certainly made life difficult for Millwall.
With just one win on their travels since the opening day of the season, at Stockport County in October, boss Kenny Jackett was determined to come up with a winning formula to improve on that wretched record.
Four changes were made to the side that had started against Southampton with Harris partnering Steve Morison up front in place of Lewis Grabban, who dropped to the bench.
In midfield Dave Martin came in for the injured Chris Hackett, whilst on the full-back front Jack Smith and Tony Craig replaced Alan Dunne and Scott Barron respectively.
Pitched against a team that had recorded just one victory in their previous nine starts, this should have been the perfect opportunity for Millwall to keep the pressure on the promotion pack with an awayday win.
But in recent seasons Oldham have proved to be something of a bogey side, and again seemed set to make it an uncomfortable afternoon for the Londoners.
With five minutes on the clock Dean Furman picked up the ball on the edge of the the 18-yard box before curling a left-footed effort wide.
Keigan Parker then wasted a great opportunity to break the deadlock after 10 minutes when a long forward ball caught the visiting defence square, but to Millwall's relief, Parker blasted high and wide of the target from 12 yards.
It was 13 minutes before The Lions registered their first shot on goal - a combination of Danny Schofield and Harris setting up Smith, whose shot was deflected for the first of three successive corners that came to nothing.
Four minutes later a quick throw from Morison picked out Schofield, and the latter's fierce angled drive was superbly tipped over by keeper Brill in the home goal.
Lions winger Martin, who seemed to be singled out by both Jim Goodwin and Deane Smalley for some rough treatment, came to the rescue with some great defensive covering work on 23 minutes to thwart Smalley after he had broken clean through into the area.
Jackett's men had a lucky let-off shortly after when Paul Robinson tumbled over and the ball fell kindly to Pawel Abbott who powered forward before wastefully dragging his shot wide from a great position.
Oldham spurned another opportunity 14 minutes before the break when Joe Jacobsen powered down the left and crossed for Smalley who hacked his shot over the bar.
As the fog descended on Boundary Park, the half-time break gave Lions boss Jackett a welcome opportunity to try and galvanise his troops to provide a ray of second-half sunshine on the pitch for the away fans.
Jimmy Abdou was inches away from providing that three minutes after the restart, striking a low effort that nearly caught out everyone, including Brill, who stood static as the ball flashed past his left hand post.
Millwall finally made the breakthrough courtesy of Harris' textbook spot-kick finish on 56 minutes, although he unfortunately hobbled off just seconds after, having clearly felt a muscle twinge when jumping for the ball.
On came Lewis Grabban, and the sub so nearly made it 2-0 14 minutes from time. Morison, who worked tirelessly up front throughout, saw his 76th-minute low shot smack the left hand post. The ball fell kindly to Grabban, but keeper Brill lived up to his name with a brilliant block to keep out a fierce follow-up shot.
Grabban then fired into the side netting having been picked out by an inch perfect Schofield pass, and Tony Craig powered a header wide from Schofield's corner as The Lions carved out a couple of decent chances.
Under-fire Oldham boss Dave Penney brought on Tom Eaves and went for broke with four, sometimes five, up front in the dying minutes.
But The Latics huffed and puffed without ever really testing keeper Forde, including a nervy five minutes of injury-time during which Millwall's dogged determination saw them hold on for three important points.
Oldham Athletic: Brill, Jacobson, Hazell, Smalley, Abbott (Brooke, 70mins), , Furman, Gregan, Parker (Eaves,83mins), Taylor, Stephens, Goodwin. Subs not used: Whitaker. Lee, Black, Ollerenshaw, Marrow.
Booking: Gregan (54mins)
Millwall: Forde, Smith, Craig, Abdou, Robinson, Ward, Martin, Trotter, Morison, Harris (Grabban, 58mins (Price, 83mins)), Schofield. Subs not used: Sullivan, Dunne, Barron, Fuseini, Laird.
Bookings: Martin (26mins), Craig (44mins), Schofield (53mins), Smith (72mins), Morison (76mins), Ward (90+3mins)
Scorer: Harris (56mins, pen)
Ref: A. Haines
Att: 3,656 (away 286)