Los Angeles let a likely victory slip away, allowing the Thunder to take a 2-0 lead in the Western Conference semifinal series. The Lakers, who were swept from the playoffs by Dallas at this stage a year ago, will host the next two games Friday and Saturday.
Andrew Bynum made a hook shot that gave the Lakers a 75-68 lead with 2:08 remaining and Los Angeles did not score another point.
Durant and Harden did all scoring from that point on, including Durant's go-ahead basket with 18.6 seconds remaining. His jumper from the baseline gave Oklahoma City a 76-75 lead and the Lakers then let the time run down before taking their final shot -- an attempt that turned out to be a misfire by Steve Blake from 3-point range.
Durant made a free throw with a second remaining for the final point of the game.
After Bynum's basket with 2:08 left, the Lakers missed three shots and turned the ball over twice. One of those turnovers came when Durant stole a pass by Kobe Bryant as the Lakers were attempting to put together a fast break.
Durant scored 22 points to lead the Thunder and Russell Westbrook had 15 in the defensive struggle. Oklahoma City shot only 42 percent and held the Lakers to 38 percent.
The teams combined to score a mere 59 points in the second half, with the Thunder outscoring the Lakers in the fourth period 17-12.
Bryant and Bynum both scored 20 points, but they hit just 17-of-44 shots from the field. The Lakers made 2-of-15 from 3-point range.