Oldham became the first team to score a league goal at Chesterfield since August when they kept up their outstanding away record to finally end a barren run.
Fitz Hall's 22nd minute header was the first goal the Spireites had conceded at home in the Second Division for 742 minutes and Oldham go into Christmas as the only club in the country to be unbeaten on their travels.
They were rarely in trouble in this game although poor finishing meant that Chesterfield always had a chance to snatch a point in the final minutes.
Wayne Andrews twice missed when through on goal and his wayward finishing could have proved costly if Mark Allott had not blazed Chesterfield's best opening over in the 62nd minute.
Chesterfield created nothing before the break but they were sharper in the second half although Latics keeper Les Pogliacomi did not have a serious save to make.
Andy Richmond, on his full debut, blocked an Andrews shot with his legs but was beaten when Hall headed a David Eyres free-kick over him and into the right-hand corner of the net.
That was enough to give Oldham their first win in nine games and manager Iain Dowie said: "The word crisis has been mumbled recently, but I have never seen it as that.
"If you can call being unbeaten away from home at Christmas a crisis then I will take that, its a fantastic achievement."