Chris Wondolowski scored in the opening half to finish the regular season tied with D.C. United's Dwayne De Rosario for the MLS scoring lead with 16 goals on the year.
San Jose also received goals from Simon Dawkins, who bagged a brace, and Rafael Baca to complete the rout, while George John and Ruben Luna pulled back consolation goals for FC Dallas.
Dawkins got San Jose off the mark in the 26th minute, blasting a shot from outside the box into the upper corner.
Baca doubled the lead just a minute later, converting on a cross to notch his first MLS goal.
Wondolowski broke through in 34th minute, slamming home a penalty kick after Steven Beitashour was fouled in the box by Jair Benitez.
Dawkins then completed his two-goal performance in the 38th minute, collecting a loose ball in the box and stuffing his effort past FC Dallas goalkeeper Chris Seitz.
FC Dallas made an effort to mount a comeback, as John made the most of a failed clearance by heading home his second goal of the year just before the break.
It took FC Dallas another 45 minutes to score, but it eventually came through an unmarked Luna, who stuffed a volley past 'Quakes goalkeeper Jon Busch to cut the deficit in half.
The loss prevents FC Dallas (15-12-7) from claiming third place in the Western Conference, meaning it will need to participate in a wild card game this week in a bid to advance to the postseason.
San Jose (8-12-14) was out of playoff contention for some time, but finishes the season in seventh place in the West, just two points above Chivas USA.