In a mixing bowl, combine cooked quinoa, black beans, corn, half of the shredded cheese, chili powder, cumin, garlic powder, onion powder, salt, and pepper.
Stuff the bell peppers with the mixture and place them in a baking dish.
Top the stuffed peppers with the remaining cheese.
Bake for 30 minutes or until the peppers are tender and the cheese is melted and bubbly.