Preheat the oven to 375 degrees F. Grease a 9-inch x 13-inch baking dish with non-stick cooking spray. Set aside.
Wash the bell peppers, cut them in half lengthwise, and remove the seeds. Arrange the pepper halves in the prepared baking dish, with the insides facing up (so you can fill them later).
Place a large skillet over medium heat and add the olive oil. Once hot, add the ground turkey and onion. Cook for 8-10 minutes, breaking up the turkey, until it is cooked through and the onions are softened.
Add the diced tomatoes with the juices from the can, taco seasoning, and garlic. Mix and cook for 1-2 minutes. Stir in the black beans, corn, and rice until evenly combined.
Divide the turkey and rice mixture evenly between the bell pepper halves. Pour 1 ounce of tomato sauce over each pepper and then sprinkle the cheese all over the top.
Cover the baking dish with foil and bake for 40-43 minutes. Remove the foil and broil for 1-2 minutes.
Carefully remove the dish from the oven and sprinkle with chopped parsley before serving warm.
Notes
If you're using homemade taco seasoning, you'll need 2 ½ tablespoons.