Preheat oven to 450º. Cut bell peppers in half, and remove seeds. Spray both sides lightly with olive oil spray. Place cut-side-down in a 9x13 baking dish. Bake 10 minutes.
In a medium bowl, combine all other ingredients with 1/2 cup of the cheese. Remove peppers from oven and scoop quinoa mixture into bell peppers. Top each with a tablespoon of shredded cheese.
Turn oven down to 350º. Cover dish with foil and place back into oven for 15 minutes, until cheese is melted and quinoa mixture is hot.
Pro tips: Spraying the underside of the foil before covering the baking dish will help the foil to not stick.