Mason Greenwood, 17, opened the scoring from close range after two minutes.
Marcus Rashford added another before half-time, when manager Ole Gunnar Solskjaer made 11 changes.
Phil Jones’ powerful header made it three, and Anthony Martial’s penalty rounded off the scoring in front of a crowd of 55,274.
Solskjaer’s side were without striker Romelu Lukaku, who is still to make an appearance on this trip after picking up ‘a knock’ in training on Tuesday.
Mason’s the man
The Belgian’s absence will only intensify discussion about his future.
And Greenwood’s performance can only embolden the growing number of people around the Old Trafford camp who feel their position would be better served by letting Lukaku join Inter Milan, who are keen on him.
Greenwood was six years of age when he first turned up at a Manchester United coaching camp in his native West Yorkshire, since when his development has been impressive.
Speaking to the English media in the team hotel on Tuesday, Solskjaer outlined Greenwood’s talents, emphasising his two-footed nature and ability to find space. “A natural finisher, a natural footballer,” was the Norwegian’s pay-off.
It was encouraging to see the position Greenwood took up to tap home Aaron Wan-Bissaka’s cross, six yards out, in the middle of the goal. It was precisely the type of run Solskjaer, a predatory finisher himself, has been telling his forwards to make, in the belief they will increase their goal tally by up to half a dozen a season.
Paul Pogba was also good for the Premier League side.
He provided the pass for Wan-Bissaka to set up Greenwood and went close with three shots from the edge of the area as he showed his class against, admittedly, limited and under-strength opponents.
Club sources are adamant they believe Pogba will remain at Old Trafford beyond the closing of next month’s transfer window, even though, yet again, the midfielder’s agent Mino Raiola has been vague about the Frenchman’s short-term intentions.
Looking at his midfield options, Solskjaer needs Pogba – without him, Scott McTominay, Nemanja Matic and Andreas Pereira do not offer much inspiration.
McTominay did supply the pass for Rashford’s 27th-minute goal, although the effort itself owed more to the England forward’s outstanding feint that took him past two Leeds defenders before a precise finish into the bottom corner.
It was Rashford’s second goal in as many pre-season games after scoring the opener against Perth Glory on Saturday.
Leeds well beaten
He landed in Perth on Tuesday, 48 hours after a 16-man squad that was minus all his new signings, including Helder Costa, apart from midfielder Jack Harrison, who spent last season at Elland Road.
Bielsa did take the rather unconventional step of watching Tuesday’s training session via wi-fi as he was still airborne. He also brought his famous bucket to sit on, although neither did Leeds much good as they were repeatedly opened up at the back.
Liam Cooper’s reckless slide into Tahith Chong that gave away the penalty from which Martial scored the fourth goal epitomised a sorry evening for the Yorkshireman, who travel to the east coast of Australia to play Western Sydney Wanderers in Paramatta on Saturday.
Manchester United fly to Singapore on Thursday where they play Inter Milan on Saturday.