Veteran winger David Eyres - at 42 the oldest outfield player in the Football League - scored for Oldham in what may prove to be his final match.
He nipped in and smartly slipped the ball into the net from close range for only his second goal of the season.
Scunthorpe threw on all three subs late on as they went all out to get back into the contest.
It worked when Billy Sharp pounced for an equaliser with a volley from six yards out two minutes from time.
Oldham: Grant, Branston, Haining, Edwards, Warne, Wellens, Eardley, Butcher (Hughes 86), Eyres (Tierney 73), Chris Hall (Taylor 66), Beckett.
Subs Not Used: Day, Forbes.
Goals: Eyres 45.
Scunthorpe: Evans, Williams (Ridley 67), Stanton, Crosby, Byrne, Beagrie (Torpey 68), Baraclough (Ryan 68), Sparrow, Taylor, Keogh, Sharp.
Subs Not Used: Goodwin, Lillis.
Goals: Sharp 88.
Ref: M Pike (Cumbria).