Salt Lake won the two-match series by an aggregate score of 2-1 after falling to the Galaxy 1-0 in the first leg of the conference semifinals.
Los Angeles was thus eliminated in its bid to win the MLS Cup for a third straight year.
Sebastien Velasquez scored in the 35th minute to tie the overall score and Nick Rimando was perfect in the Salt Lake goal the rest of the way.
Schuler scored in the 102nd minute off a free kick from Javier Morales. The Morales kick came from near the sideline and sailed across the front of the goalmouth. As it reached the far post, Schuler was there to nudge it home.