Cook quinoa according to package directions. Remove from heat and cool completely before assembling salad.
Add oil to a non-stick pan. Sear tempeh until golden brown.
Combine quinoa, bell peppers, onion, cucumber, pepperoncinis, olives, garbanzo beans, and feta (if using) in a large salad bowl. Toss with dressing and some liquid from the pepperoncini jar.
To assemble salad, place a bed of spinach in a bowl, add quinoa mixture and tempeh on top. Enjoy!