The 19-year-old midfielder has so far made 12 starts for the Latics since joining the club on an initial one-month loan deal in August.
Oldham boss Dave Penney said: "We're absolutely delighted both with the way Alex has played and to have him here until the end of the season.
"Alex has done really well since he came in. He's showed his versatility by not only playing in his more natural position in the centre of midfield but also at right-back for us."
Meanwhile, Penney will scour the loan market again for a striker as Pawel Abbott recovers from a hernia operation.