The Huddersfield winger touched down twice, taking his total to 11 tries in 10 appearances, and put his centre Kallum Watkins over for two others as Wayne Bennett’s men repeated the scoreline from their final group game against France a week earlier.
England were once more far from perfect but, after watching New Zealand slip up in their quarter-final, will be relieved to get through a bruising battle to set up a showdown with Tonga in Auckland next Saturday.
McGillvary, who has now scored six tries in four World Cup matches, was the stand-out performer but there were also notable contributions from Watkins, who at last demonstrated his class on the international stage, and St Helens duo Alex Walmsley and James Roby.
The Kumuls were unfortunate to lose captain David Mead in the second minute after he took a head knock while halting a darting run from Luke Gale which meant Stargroth Amean stepped into the full-back role after initially being on standby for winger Garry Lo.
And the Pacific Islanders ought to have taken the lead when centre Kato Ottio leapt above full-back Gareth Widdop to collect the ball from Watson Boas’ high kick only to lose the ball over the line.
A 40-20 kick from Josh Hodgson helped turn around the early momentum and PNG needed to pull off two interceptions to halt dangerous attacking moves before McGillvary took centre stage, to the delight of the England fans among the 10,563 crowd at the Rectangular Stadium in Melbourne.
Widdop and Watkins combined to get him over after 12 minutes and seven minutes later the Leeds centre produced a sublime pass for McGillvary’s second.
Widdop was unable to convert either try and England had to wait until the 33rd minute to add to their points tally, giant substitute Walmsley proving unstoppable from 10 metres out as he carried three defenders over the line with him to score his first international try.
This time Widdop kicked the goal to make it 14-0 and Ottio had a second try disallowed just before the interval when he was ruled to have pushed Widdop off the ball as he chased Boas’ kick to the corner.
It was another promising position for England but it took them some time to make their obvious superiority count.
Prop James Graham was denied a try early in the second half for a forward pass and there was another flurry of handling errors before a surging run out of defence by winger Ryan Hall created the position for Widdop, demonstrating his rugby brain, to kick ahead for substitute second rower Ben Currie to touch down.
Widdop’s second goal made it 20-0 but the Kumuls grabbed a deserved score on the hour when second rower Willie Minoga crafted a try for the Castleford-bound Lo and Rhys Martin added the goal.
England knew they had been in a game but they produced a strong finish, with McGillvary breaking clear to get Watkins over for his first try and then collecting Gale’s high kick to put him in for a second.
Hall then put the seal on the win with England’s seventh try and Widdop kicked his fourth goal to complete a satisfactory evening for his side.