Step 1: Preheat your oven to 375°F (190°C). Cut the tops off the bell peppers and remove the seeds and membranes. Rinse them thoroughly.
Step 2: In a large skillet, brown the ground beef over medium heat until no longer pink. Drain the excess fat.
Step 3: Add the diced onion and garlic to the skillet with the beef. Sauté for 3-4 minutes until the onions are soft and translucent.
Step 4: Stir in the cooked rice, half of the tomato sauce, oregano, salt, and pepper. Mix well until everything is evenly coated and heated through.
Step 5: Stand the peppers upright in a 9×13 inch baking dish. Spoon the meat and rice mixture into each pepper until they are full.
Step 6: Pour the remaining tomato sauce over the tops of the stuffed peppers. Cover the dish tightly with aluminum foil.
Step 7: Bake for 35 minutes. Remove the foil, sprinkle the shredded cheddar cheese over the peppers, and bake for an additional 10 minutes or until the cheese is melted and bubbly.
Step 8: Let the peppers rest for 5 minutes before serving to allow the juices to settle.