Cook quinoa according to package instructions.
Preheat oven to 375 degrees F and lightly grease a large baking dish or rimmed baking sheet.
Brush halved peppers with olive oil.
Add cooked quinoa to a large mixing bowl and add the tomatoes, nutritional yeast, chili seasoning, sea salt, black beans, and corn. Mix to combine thoroughly.
Generously stuff halved peppers with quinoa mixture until all peppers are full, then cover the dish with foil.
Bake for 25 minutes covered. Then remove foil, increase heat to 400 degrees F and bake for another 25-30 minutes, or until peppers are soft and slightly browned.
Serve with plant-based sour cream and cilantro.