Fosu made his first-team debut from the bench on the final day of last season during Reading’s win over Derby and impressed as he forced goalkeeper Lee Grant into making a number of saves.
The 19-year-old came through the youth ranks at the Madejski and played a key role in helping Reading’s U21s win promotion to the Premier League Division One last season.
“I’m delighted to have signed,” Fosu said on Reading’s website. “Another two years and now I’m looking to kick on from last season and hopefully serve the club well.
“I’m still buzzing now ever since making my first team debut on the last day of the season. It was an unexplainable feeling and I thought I took my chance well. I like to excite the fans. I’ve just got to do what I do and hopefully they enjoy it.
“I would like to make my mark on the first team this season. But I’ll keep my feet on the ground, keep working hard and hopefully I’ll get the opportunity.?”