LOS ANGELES, 29 Aug 2016, (AFP) - The 26-year-old Reed caught and passed 54-hole leader Rickie Fowler who stumbled to the finish by playing his final four holes in three over.
Fowler failed to make the US team and will have to rely on a captain's pick when Davis Love makes his final four selections in the coming weeks.
"It is awesome," said Reed, who earned $1.5 million for his first win of 2016.
"I worked hard with my coach the last couple weeks so it shows I am moving in the right direction.
"I am glad I was finally able to close one off."
Reed finished at nine-under 275 for a one-stroke victory over Sean O'Hair (66) and Argentina's Emiliano Grillo (69), who tied for second.
Top-ranked Jason Day of Australia (69) was two strokes back and tied for fourth with Gary Woodland (69) and world number seven Adam Scott of Australia (71) at the Bethpage Black course in Farmingdale, New York.
Fowler (74) was three strokes back and tied for seventh with Ryan Moore and Jason Kokrak, who each carded 69s.
World number three Jordan Spieth (69) tied for 10th with Justin Thomas (71) at four shots behind.
The Barclays marked the start of the PGA Tour playoffs but it also signalled the end of the Ryder Cup qualifying for the Americans.
Dustin Johnson, Spieth, Phil Mickelson, Jimmy Walker and Brooks Koepka already made the team. Reed, Brant Snedeker, Zach Johnson rounded out the team when the points standings closed on Sunday.
World number 14 Reed bolstered his chances by being the 18-hole leader and then holding the outright lead at 36 holes.
His mixed bag round on Sunday included four birdies and three bogeys.
Love will announce three of his four Ryder Cup captain's picks September 12 and save his fourth and final pick for September 25th.
"We have an extremely talented group of eight automatic qualifiers for this year's US Ryder Cup team," Love said. "Each has a real passion for the Ryder Cup."
The European team consists of four players from a European Tour money list along with five from a list of world ranking points.
Rory McIlroy, Danny Willett, Henrik Tenson and Chris Wood are in by virtue of the money list, while Sergio Garcia, Justin Rose, Rafa Cabrera Bello, Andy Sullivan and Matt Fitzpatrick secured spots through the world rankings.
Clarke is due in the coming days to announce his three captain's picks for the tournament, which begins next month in Minnesota.
The top 100 players in the FedEx Cup standings advance to next weekend's Deutsche Bank Championship, the second playoff event at the 7,207-yard, par-71 course in Boston, Massachusetts.
Leading scores after final round of The Barclays Championship USPGA Tour event on Sunday (par-71, US unless stated):
275 - Patrick Reed 66-68-71-70
276 - Sean O'Hair 69-69-72-66, Emiliano Grillo (ARG) 67-69-71 69
277 - Jason Day (AUS) 68-70-70-69, Gary Woodland 71-69-68-69, Adam Scott (AUS) 69-72-65-71
278 - Ryan Moore 69-68-72-69, Jason Kokrak 74-66-69-69, Rickie Fowler 67-69-68-74
279 - Jordan Spieth 71-67-72-69, Justin Thomas 71-71-66-71