Kevin Durant flirted with a triple double while making the Thunder the first NBA team to reach 40 victories this season.
The game was tied at 77-77 when Fisher hit a 3-pointer in the final seconds of the third period. Lamb then began the fourth quarter with another long-range shot and Oklahoma City went on to build an 89-77 advantage.
Durant had 26 points, nine rebounds and seven assists. Reggie Jackson added 20 points and nine assists for the Thunder. It was Oklahoma City's 12th win in 13 games and the Thunder's ninth straight victory on Minnesota's home floor.
Ricky Rubio led Minnesota with 19 points and eight assists. The Timberwolves were without All-Star forward Kevin Love, who missed the game with a stiff back.