Scott, leading the Aussie charge at the testing Pennsylvanian course, was right in the thick of the early hunt for the clubhouse lead on Thursday as, starting from the 10th hole, he reached the turn in two under.
But dropped shots at the third and eighth holes - his 12th and 17th - dragged the 44-year-old former Master back to level par, four shots adrift of the early pacesetter, American J.J. Spaun, who recorded a superb bogey-free 66.
Among the early wave, Scott, competing in a remarkable 96th consecutive major championship dating back to the 2001 British Open at Royal Lytham & St Annes, was still in a top-10 position as Oakmont began to bare its teeth.
Scott's round was a topsy-turvy affair from the start, as he recorded three bogeys and five birdies in his first nine holes, but as often has been the case in recent years, he was unable to prevent an accident-prone finale.
Yet the 2013 Masters champion still enjoyed a much better start than the current green jacket holder Rory McIlroy, who ended up eight shots back after a four-over 74.
Australia's 'two Cams' both suffered disappointing starts, with Cameron Davis also shooting a 74, while Cameron Smith couldn't muster a single birdie in a 75 that featured five bogeys.
The pre-tournament talk had been all about how challenging the Oakmont Country Club course would be but Spaun produced a remarkable effort, only the eighth bogey-free round ever in a US Open there.
The 34-year-old Spaun, who lost to McIlroy in a play-off at The Players Championship in March, recorded his lowest ever round in a major in stifling early conditions.
South Korean Kim Si-woo, whose birdie attempt at his final hole just missed, finished two shots off the pace while American Ben Griffin was a further shot adrift after mixing three birdies with two bogeys.
Spaun, who started on the back nine, had a spectacular start reaching the turn with four birdies to become the first player ever to cover the first nine in the opening round of an Oakmont US Open in 31 strokes or fewer.
Defending champion Bryson DeChambeau, looking to become the first repeat US Open winner since Brooks Koepka in 2018, struggled in the penal rough to go round in 73.
But McIlroy's bright start, as he made two early birdies, ended up giving way to a wayward second nine as he made four bogeys over a seven-hole stretch.
The most dramatic shot of the day was Patrick Reed's amazing second on the 621-yard fourth hole, which the former Masters champ holed from 286 yards for only the fourth albatross in US Open history.
Tournament favourite Scottie Scheffler was going out with the late starters alongside two-time major winner Collin Morikawa and European star Viktor Hovland.
With agencies
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