James Wesolowski scored the only goal as Oldham beat Stevenage to earn their first win in seven league games.
The unmarked midfielder settled a scrappy game when he headed home Mike Petrasso's cross from eight yards.
Earlier, Stevenage's Jon Ashton headed against a post and Latics keeper Mark Oxley had to make several smart saves.
But Stevenage could not find a breakthrough and lost Ben Chorley to an 86th-minute red card for an off-the-ball clash with Jonson Clarke-Harris.
VIEW FROM THE DRESSING ROOM
Oldham manager Lee Johnson told BBC Radio Manchester:
"It was a fantastic performance because we got a clean sheet.
"We had one moment in the first half that was a bit scary where it hit the post but apart from that we were solid.
"If we were a little bit better at finishing maybe we could of won by more.
"There's always pressure because we feel that we're not in as high a position as we want, but this was a particularly big game."
Stevenage manager Graham Westley told BBC Three Counties Radio:
"I didn't think there was a deserved winner in the game, but obviously they got the one goal that won it in the first half.
"If you look at the two goalkeepers, they were both dramatically under worked. They got their goal, we hit the post, that aside the two goals weren't really threatened.
"They were determined to hang onto their lead and sat quite deep with their defence and made it quite difficult for us.
"I didn't see [Ben Chorley's sending off]. The footage isn't very clear of the incident, the players were adamant that the centre-forward had stamped. I can't comment, I don't know what went on."
Oldham Athletic 01 Oxley 05 Kusunga 12 Mellor 08 Smith 06 Tarkowski 03 Grounds 20 Petrasso (Rooney - 89' ) 04 Wesolowski 14 Clarke-Harris (MacDonald - 89' ) 27 Philliskirk 30 Harkins (Dayton - 74' ) Substitutes 02 Brown 09 Rooney 10 MacDonald 17 Rodgers 18 Lockwood 19 Dayton 29 Rachubka Stevenage 16 Day 06 Jones Booked (Andrade - 80' ) 29 Hartley 02 Wedgbury (Doughty - 45' ) 04 Chorley Dismissed 05 Ashton 07 Morais 13 Parrett 19 Haber (Charles - 61' ) 12 Zoko 15 Freeman Substitutes 09 Charles 10 Burrow 20 Smith 21 Tounkara 24 Doughty 25 Andrade 26 Smith
Ref: Steven Rushton