Place one medium bell pepper on cutting board, laying bell pepper on its side. Cut away top and stem of bell pepper and discard.
Carefully slice through ribs of bell pepper to separate core from inner edges of pepper.
Pull core out of bell pepper, then use metal spoon to scrape out any seeds or remnants of core.
Repeat process until all 6 medium bell peppers have been hollowed. Place hollowed peppers upright in 9x13 casserole dish, then set aside.
Preheat oven to 350° Fahrenheit.
For the Filling
Place large skillet on stovetop over medium-high heat. Add 1 tablespoon avocado oil to skillet and heat pan until oil is hot and shimmery.
When oil is hot, add ½ cup chopped onion and 1 tablespoon minced garlic to skillet. Sauté ingredients, stirring often, approximately 5 minutes or until onions have softened.
Add 1 pound ground turkey to skillet. Cook turkey, stirring frequently and breaking up meat with wooden spoon, until turkey is browned and crumbled, approximately 15 minutes.
Once turkey is browned, carefully drain liquid from skillet, then return skillet to heat.
Add 1 10-ounce can diced tomatoes and green chilies, 2 tablespoons taco seasoning, salt (if seasoning doesn't include any), and ¾ cup water to skillet. Stir ingredients together until incorporated.
Bring mixture to boil, then immediately reduce heat under skillet to low. Simmer mixture over low heat, stirring occasionally, 10 to 15 minutes or until thickened.
Remove skillet from stovetop and let mixture cool slightly. Add 1 cup shredded Mexican cheese blend, 1 cup cooked rice, 1 cup frozen corn kernels, and 1 15-ounce can black beans to skillet. Stir to incorporate.
Return skillet to heat and stir ingredients together until cheese has melted.
Once cheese has melted, portion ground turkey filling into prepared peppers, filling each pepper only halfway.
Divide 1 cup shredded Mexican cheese blend in half. Set ½ cup shredded cheese aside. Divide remaining cheese evenly between peppers, covering filling completely.
Portion remaining ground turkey filling into peppers, filling peppers completely. Top each pepper with reserved ½ cup shredded cheese.
Once peppers are completely filled and topped with cheese, pour 1 cup water into casserole dish, surrounding bell peppers with shallow pool of water. Do not pour water on top of or into bell peppers.
To Bake the Stuffed Peppers
Cover dish with aluminum foil, then place dish in preheated oven. Bake peppers 25 minutes.
After 25 minutes, carefully remove baking dish from oven. Remove and discard aluminum foil.
Set oven to Broil, then carefully return casserole dish to oven. Broil peppers approximately 5 minutes or until cheese is just melted and lightly browned.
When satisfied with color of cheese, carefully remove baking dish from oven. Portion stuffed peppers onto serving plates as desired. Serve warm.
Recipe Notes
Ground Turkey: Leaner turkey will be less greasy, but can overcook easily.
Make-Ahead Option: Prepare this recipe as instructed. After covering the baking dish with aluminum foil, place the dish in the refrigerator. Refrigerate up to 24 hours. Allow peppers to come to room temperature before baking, or increase bake time if baking peppers from cold.