JERSEY CITY, August 23, 2013 (AFP) - Stadler had a one-stroke lead over Sweden's Henrik Stenson, Ryan Palmer and Colombian Camilo Villegas.
It was a further stroke back to Australian Jason Day and American Matt Kuchar on 66.
World number one Tiger Woods, whose five victories this season sent him into the playoffs atop the points standings, also played without a bogey, posting a four-under 67 at Liberty National Golf Club.
He was tied in the clubhouse with Zimbabwe's Brendon de Jonge, Canadian Graham DeLaet and fellow Americans Nicholas Thompson, Matt Every and Morgan Hoffman, while Harris English was also at four-under having played just six holes.
Two weather delays lasted a total of five hours and 51 minutes. No one who teed off in the afternoon played more than nine holes and some completed only two.
Stadler knew he was in for a long wait before he'd have a chance to start round two and try to build on his lead.
But he was pleased to have completed the opening round.
"I don't know what time we are going to start tomorrow," he said. "It's going to be late. But I prefer to be on this side where we don't have a marathon day ... it won't take as big of a toll as the other guys."
Woods, showing no sign of the sore shoulder and neck he spoke of early in the week, hit 13 of 18 greens in regulation. He teed off on 10 and birdied three straight holes starting at the 14th, then picked up one more bogey at the par-three fourth.
He capped his round with a par-save from the greenside rough at the ninth.
Partial scores on Thursday in the weather-disrupted first round of The Barclays, $8 million opening event in the US PGA Tour playoffs (darkness halted play, round to resume Friday. USA unless noted, par-71)
64 - Kevin Stadler
65 - Ryan Palmer, Henrik Stenson (SWE), Camilo Villegas (COL)
66 - Jason Day (AUS), Matt Kuchar
67 - Nicholas Thompson, Brendon de Jonge (ZIM), Graham DeLaet (CAN), Tiger Woods, Matt Every, Morgan Hoffmann
68 - Nick Watney, Josh Teater, Brian Gay, Charley Hoffman, Charl Schwartzel (RSA), Justin Rose (ENG), Geoff Ogilvy (AUS), Jeff Overton, James Hahn, Carl Pettersson (SWE)