Jonathan Grounds' second-half winner at Swindon earned Oldham their first victory away from home since November.
Latics keeper Mark Oxley saved Swindon's solitary first-half effort on goal from a Ryan Harley free-kick.
New arrival Jon Stead
went close with a header before setting up the winner, Grounds firing in the rebound after the Latics substitute's shot was blocked.
Swindon finished with 10 men after half-time sub Troy Archibald-Henville was sent off for a second yellow card.
VIEW FROM THE DRESSING ROOM
Swindon Town manager Mark Cooper told BBC Wiltshire:
"We needed to compete. It wasn't a day for pretty football.
"I would suggest that they wanted it more, which is the disappointing thing.
"We made one or two changes. The only positive for me was Troy Archibald-Henville. He was outstanding when he came on.
"I thought the referee was poor but I'm not going to use that as an excuse."
Oldham manager Lee Johnson told BBC Radio Manchester:
"We've come to a tough place in tough conditions and I think we've won the day - tactically, technically and effort wise.
"We've just chucked that back four together. We've done two days of work on it, which isn't enough work for any back four, but sometimes when you do that it ends up working well.
"[The transfer window] has been hectic. I think i've got to give my phone a massage on Monday because it's been overworked that much.
"We're working with a small budget so we've got to wheel and deal even more, and that's why I'm really pleased with the business that we've done."
Swindon Town 01 Foderingham 02 Thompson 34 Reckord 04 Luongo (Gladwin - 72' ) 22 Ward (Archibald-Henville - 45' Dismissed after an earlier booking ) 29 Branco Booked 03 Byrne 07 Harley 28 Smith Booked 19 Thompson 33 Barker (Ranger - 59' ) Substitutes 06 Reis 09 Ranger 21 Smith 23 Barthram 25 Belford 39 Gladwin 41 Archibald-Henville Oldham Athletic 01 Oxley 02 Brown 03 Grounds 04 Wesolowski 16 Wilson 18 Lockwood 28 Worrall Booked (Kissock - 89' ) 08 Smith 27 Philliskirk 14 Clarke-Harris (Stead - 64' ) 30 Harkins Substitutes 09 Stead 12 Mellor 17 Rodgers 19 Dayton 20 Kissock 21 Millar 29 Rachubka
Ref: Tim Robinson