Westbrook netted 28 points on 12-for-25 shooting while Durant added 25 with 10 rebounds for the Thunder, who closed out their Western Conference semifinal series 3-games-to-1.
James Harden added 17 points and eight rebounds off the bench as Oklahoma City defeated the Lakers in a post-season series for the first time since 1979 when the franchise was known as the Seattle SuperSonics.
They had lost six straight series to Los Angeles in the interim.
Kobe Bryant poured in 42 points for the Lakers, going 18-for-33 from the field.
Forward Pau Gasol grabbed 16 rebounds but managed only 14 points in the loss.