Preheat your broiler to high. Using about 1 Tablespoon of olive oil, rub peppers with the oil and place on a baking pan. Broil until the outside of the pepper is blistered, turning the pepper halfway, about 10-15 minutes, total. Remove from oven and place them into a bowl. Cover the bowl tightly with plastic wrap and let sit for 10 minutes. Remove the peppers from the bowl and remove the skins. Cut the peppers in half and remove the seeds. Set peppers aside. Preheat oven to 350ºF.
Meanwhile, prepare the quinoa by combining the quinoa, chicken stock, and 1/2 cup of water. Bring to a boil, cover, and reduce heat to low. Cook 15-20 minutes. Remove from heat and let sit for 5 minutes.
In a large skillet heat the rest of the oil to medium heat. Add the onion and garlic and cook until tender, about 5-6 minutes. Remove from heat. Pour the quinoa into the skillet along with the corn, beans, chili powder, cumin, salt, and pepper. Stir to combine.
Place the halved peppers on a baking sheet and stuff with the quinoa mixture. Top with shredded cheese and bake until hot and cheese is melted, about 15 minutes. Remove from oven and garnish with cilantro. Serve.