Christian Maghoma's unfortunate own goal and a close-range header from Rowan Liburd saw Reading go in at the break two goals to the good.
And it got worse for us just before the hour mark when Tariqe Fosu was clipped by Kyle Walker-Peters and scored the resulting penalty to increase the visitors' lead.
Substitute Anton Walkes pulled one back for us, but Liburd netted again soon afterwards to complete the scoring.
Spurs U21s: Glover; Walker-Peters, Carter-Vickers (c), Maghoma, Lesniak; Amos, Veljkovic (Edwards 78); Sonupe, Goddard (Walkes 57), Georgiou (McEvoy 63); Harrison. Substitute (not used): Voss (GK).
Reading U21s: Moore; Long, Hyam, Sweeney (c), Griffin; Fridjonsson, Kelly; Semedo (Husin 71), Novakovich, Fosu; Liburd (Rinomhota 78). Substitutes (not used): Jules, Owusu, Ward (GK).