Preheat oven to 350°F. Spray baking dish with nonstick cooking spray. Choose a dish that will accommodate 6 filled peppers.
Prepare peppers: Bring a large pot of salted water to boil over high heat. Wash peppers and cut off tops. Discard seeds and ribs. Submerge peppers in water and boil for 3 minutes. Using tongs or slotted spoon, carefully remove peppers and let cool upside down on wire rack, until you are able to handle them..
Prepare filling: In a large bowl, mix together all other ingredients. Save ¼ cup of the cheese to sprinkle on top of the peppers.
Filling the peppers: Set peppers upright in prepared baking dish. Fill peppers with filling, pushing down gently and heaping up slightly on top. Sprinkle with reserved cheese.
Bake at 350°F for 40 to 45 minutes or until browned on top and heated through.
Serve with additional chopped fresh cilantro, salsa, sour cream, or avocado.
Not a fan of quinoa? Substitute cooked white or brown rice.
Any type of tomato can be used. If they are large, dice them. Canned diced tomatoes can be substituted; drain slightly before using.
Use any kind of chicken you happen to have, including canned chicken. Taco meat or cooked ground beef can be substituted.