Buttler's 110 not out featured nine sixes, including a straight drive off Hasan Ali that took him to three figures.
Such was his command that Buttler's second fifty took him a mere 18 balls, with new father Buttler making a 'rocking the baby' gesture to celebrate bringing up a century that also included four fours.
An extraordinary 'inside out' six off Hasan over long-off was arguably the pick of his shots, although a pull off Shaheen Shah Afridi that cleared the rope and took him into the 90s was almost as impressive.
It was an encouraging display by the World Cup hosts just a few weeks from the start of the tournament and further proof of their progress as an ODI side.
Saturday's total was the 35th time since their miserable first-round exit at the 2015 World Cup that England, now top of the ODI rankings, had posted a total in excess of 300 -- a feat they had achieved only 34 times in total prior to that tournament.
Earlier, Jason Roy (87) and Jonny Bairstow (51) laid a platform for the innings with an opening stand of 115 after Morgan won the toss.
Roy, fit following back trouble that kept him out of Wednesday's washed out opener of a five-match series at his Oval home ground, hit medium-pacer Faheem Ashraf for two huge sixes -- a drive over long-on followed by an extravagant uppercut over extra-cover.
But the return of left-arm quick Afridi for a second spell saw Pakistan make the breakthrough.
Bairstow pulled him for a boundary to complete a 44-ball fifty. But the next ball saw Bairstow fail to pull down and a leaping Fakhar Zaman at deep backward square leg held a good catch at the second attempt.
Following a brief rain break, Roy fell in sight of what would have been his eighth ODI hundred when he miscued a pull off Hasan to mid-on. Test captain Joe Root made 40 before he holed out, his exit paving the way for Buttler's blistering innings.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)