Garcia's 6-under, fired over the Liberty National Golf Club course, left him tied for the top spot with Paul Goydos and Steve Marino.
Charley Hoffman, Webb Simpson, Fredrik Jacobson and Heath Slocum were all at 66.
Tiger Woods, who begins the playoffs with the lead in the FedEx Cup points race, settled for a 1-under 70 and was tied for 27th place. Phil Mickelson also had a 70.
A change in the points system for this year's playoffs creates an opportunity for golfers to make dramatic moves in the standings. There are five times more points available for the playoff events than there were for regular tournaments this season and the winner this week will earn 2,500 points.
Garcia, for instance, began this week in 89th place, but a win at The Barclays could vault him all the way to second.
The points leader at the end of the four playoff tournaments will win $10 million.
Garcia had the lead until he missed a 12-foot par putt on his final hole.
"Even though the greens are soft, I didn't expect to see three 65s out there," Garcia said. "It is a good, solid course with small greens. I've always liked that kind of golf. If you play decent, you're going to have a chance at making birdies."