Preheat the oven to 375°F (190°C).
Cut the tops off the poblano peppers and remove the seeds.
In a skillet, sauté diced onion and minced garlic until fragrant.
Add the ground beef or turkey to the skillet, cooking until browned.
Stir in cooked rice, black beans, corn, cumin, chili powder, salt, and pepper.
Mix in half of the shredded cheese until melted.
Stuff each poblano pepper with the meat and rice mixture.
Place stuffed peppers in a baking dish and top with remaining cheese.
Cover with foil and bake for 20 minutes.
Remove foil and bake for an additional 10 minutes until cheese is bubbly.