In a small pot, bring quinoa and chicken stock to a boil. Stir, cover and reduce heat to simmer until cooked, about 20 minutes.
While quinoa is cooking, saute onions and sweet potato in olive oil over medium heat. Cook 7 minutes, stirring frequently until sweet potato has softened. Stir in garlic, cook another minute then remove from heat. Pour into large bowl.
Pour cooked quinoa into bowl with onions and sweet potato, along with chicken, cumin, salsa and scallions. Stir until combined.
Preheat oven to 375 degrees.
Cut bell peppers in half, scoop out seeds and place on baking sheet. Stuff each pepper with quinoa filling and top with cheese.Bake 30-40 minutes or until the pepper is cooked to your liking. Serve hot.