Step 1: Preheat the oven
Preheat your oven to 400°F (200°C).
Step 2: Prepare the bell peppers
Cut the tops off the bell peppers and remove the seeds and membranes.
Rinse the peppers thoroughly. If necessary, trim a very thin slice from the bottom of each pepper so it can stand upright without cutting through the base.
Set the prepared peppers aside.
Step 3: Cook the ground beef
Heat a large skillet over medium-high heat.
Add the ground beef and chopped onion. Cook for approximately 7–10 minutes, breaking the beef into small pieces as it browns.
Continue cooking until the beef is fully browned, the onion is softened, and the meat reaches a safe internal temperature of 160°F (71°C).
Drain any excess fat.
Step 4: Prepare the filling
Add the cooked rice, Italian seasoning, garlic powder, salt, and black pepper to the skillet.
Stir everything together until the beef, rice, and seasonings are evenly combined.
Step 5: Prepare the baking dish
Pour one 15-ounce can of tomato sauce into the bottom of a 9-inch square baking dish.
Spread the sauce evenly to create a flavorful base for the peppers.
Step 6: Stuff the peppers
Spoon the beef and rice mixture into each prepared bell pepper.
Fill the peppers generously, gently pressing the mixture down to distribute it evenly.
Arrange the stuffed peppers upright in the baking dish.
Step 7: Add the tomato sauce
Pour the remaining can of tomato sauce over the stuffed peppers, allowing some of the sauce to run down their sides.
Cover the baking dish tightly with aluminum foil.
Step 8: Bake the peppers
Bake the Italian Stuffed Peppers for 35–45 minutes, or until the bell peppers are tender.
Cooking time may vary depending on the size and thickness of the peppers.
Step 9: Add the mozzarella
Carefully remove the aluminum foil.
Sprinkle the shredded mozzarella cheese evenly over the tops of the peppers.
Return the baking dish to the oven, uncovered, and bake for another 5 minutes, or until the cheese is completely melted.
Step 10: Serve
Remove the baking dish from the oven and allow the peppers to rest for a few minutes.
Cut each stuffed pepper in half and spoon the warm tomato sauce from the baking dish over each portion.
Serve warm.