Preheat oven to 400 degrees.
Cook quinoa according to package instructions.
While quinoa is cooking, add oil to skillet over medium heat and saute peppers and onion until tender.
Add beans, corn, quinoa, 1 can enchilada sauce, and a handful of cheese to skillet. Mix to combine and heat through.
Add remaining can of enchilada sauce to 9x13" baking dish and spread evenly across bottom.
Pour casserole mixture into baking dish, spreading evenly as well, then top with shredded cheese to cover.
Place in the oven for 10 minutes, or until cheese is melted and beginning to brown.
Remove from oven and serve.