Cut peppers in half, remove seeds and tails. Place in 1-2 large baking dishes to fit and set aside. Preheat oven to 400 degrees F.
Preheat large skillet on medium-high heat and swirl oil to coat. Add ground turkey, onion, garlic and saute for 5 minutes, stirring often and breaking into pieces.
Transfer cooked meat to a large bowl and add black beans, corn, rice, taco seasoning, cumin, salt, pepper and half tomato sauce. Stir well to combine.
Stuff peppers with meat rice mixture and spoon remaining tomato sauce on top.
Bake for 35 minutes, sprinkle with cheese and bake for a few minutes until cheese has melted.
Remove from the oven and sprinkle with parsley or green onion.
Serve with plain yogurt or sour cream.
Notes
Store: Refrigerate leftovers for up to 5 days in an airtight container. Reheat in microwave or place in a pot with a splash of water, cover and simmer for 5-10 minutes until steamed through.
Freeze: Do not freeze as peppers will become too watery when thawed.
Make ahead: You can refrigerate stuffed peppers without cheese covered for up to 24 hours. Make sure to let stuffing cool before refrigerating and dish warm up on a counter for 10 minutes before baking. I would add 5-10 minutes to cook time.