It is understood that Oldham were keen to keep the 19-year-old at the club, but boss Lee Johnson has revealed that Obika has now returned to his parent side.
"I have spoken to Jordan and he has enjoyed his time here. Reading have a new manager (Nigel Adkins) and Jordan is keen to go back and impress him," Johnson told the club's official website.
"I would like to thank Jordan for his service and also to his parent club for allowing him to join us."
Obita made 10 appearances for the Latics.