Pre-heat oven to 350 degrees. Spray a 9x9 inch baking dish with non-stick cooking spray. Wash peppers, and cut around the stem to remove. Remove the seeds and ribs inside the peppers. Set peppers on baking pan.
Meanwhile, spray a large pan with cooking spray, and turn the heat up to medium high. Add the ground turkey, seasonings, and green chiles to the pan. Cook until the meat is no longer pink.
Add the beans, corn, and salsa to the skillet with the turkey and stir until everything is combined. Remove from heat.
Spoon the turkey mixture evenly into the 4 peppers and sprinkle 2 tbs diced tomatoes (if using) and 2 tbs cheese on top of each one.
Bake, uncovered, for 30-35 minutes, or until peppers are tender. and remove from the oven. Top with green onions if desired.