Salt Lake, which came into the second leg of the West final with a 4-2 lead in the aggregate-goal series, increased that advantage when Findley tapped in the rebound of a shot off goalkeeper Donovan Ricketts in the 28th minute.
With the victory, RSL advances to the Dec. 7 MLS Cup final on the road against Sporting Kansas City. It will be seeking its second MLS championship after taking the honors in 2009 in its only other trip to the title game.
The Timbers, meanwhile, lost at home for the first time since March. They fell short in a bid for the championship in their first-ever post-season appearance.