Second-half goals from Reading's Danny Loader and Ben House handed Southampton a 2-0 loss, their first PL2 defeat of the season.
Loader, PL2’s August player of the month, opened the scoring on 64 minutes and the lead was doubled by House 14 minutes later at Madejski Stadium.
The win lifts Reading to third in Division 2 on 12 points. Southampton are two places and a point behind.
See: Southampton report