The class is headlined by the fifth-ranked recruit in the country.
Freddie Dilione V had 19 points for the Nittany Lions.
Stewart connected on six of his eight attempts from three-point range on Saturday.
Melih Tunca led Penn State with 19 points in the win.
Neither team has a Big Ten win this season.
Melih Tunca won Young Player of the Regular Season honors in the Turkish Basketball Super League last season.