The 23-year-old striker started the rout in the 13th minute when he took a first touch from an Andreas Pereira pass before slamming home and quickly made it 2-0 after some lovely lead-up work from Memphis Depay.
Early in the second half, Keane completed his hat-trick when receiving another pass from Memphis before lofting home before Pereira made it 4-0 when slotting home from the penalty spot soon after.
Keane then produced the goal of the night just before the hour-mark with an outstanding chip and then Tim Fosu-Mensah got in on the act with his first goal at U21 level, racing onto a Memphis through ball to rifle home.
Former Preston North End loanee Keane added a fifth courtesy of some impressive work from skipper James Weir to complete the demolition.
It was a stunning performance from the ex-England U21 international who cannot be far away from getting a chance in Louis van Gaal's first team while Memphis, with three assists, put his name forward for a starting recall.
Check out Keane's brilliant fourth goal courtesy of MUTV below:
U21s: Five goals tonight for Will Keane. None better than this beauty... #mufchttps://t.co/nJRsADysAW
— Manchester United (@ManUtd) February 8, 2016