Wealdstone won 2-1 at Boundary Park to deliver Oldham’s first defeat of the National League season.
Rhys Browne tapped home Jack Cook’s header to give the visitors a 10th-minute lead.
Wealdstone doubled their lead seven minutes later when Browne picked out Tarryn Allarakhia, who slotted home in confident fashion.
Cook saw an effort cleared off the line but Oldham were back in the contest seconds after the restart when Ben Tollitt crashed a fierce shot off the crossbar.
Oldham thought they had rescued a point 20 minutes from time, but Mike Fondop’s effort was ruled out for offside.
Subscribe or register today to discover more from DonegalLive.ie
Buy the e-paper of the Donegal Democrat, Donegal People's Press, Donegal Post and Inish Times here for instant access to Donegal's premier news titles.
Keep up with the latest news from Donegal with our daily newsletter featuring the most important stories of the day delivered to your inbox every evening at 5pm.