Preheat oven - Preheat oven to 375°F and spray two large baking pans with non-stick cooking spray. Set aside.
Boil water - Bring a large pot of water to a boil over high heat. As the water comes to a boil, prepare your sauce.
Brown the ground beef - Add 1 teaspoon of olive oil to a large heavy-bottomed Dutch oven or saucepot set over medium-high heat. Brown the ground beef and sprinkle with salt and pepper, to season. Transfer beef to a clean plate and set aside.
Cook the onions and garlic - Add the remaining teaspoon of olive oil and return to medium heat. Add the onions and cook for 5 minutes, or until soft and translucent, stirring often. Stir in the minced garlic. Cook, stirring continuously, for 1 minute.
Add the tomato paste and seasoning - Add the tomato paste to the vegetables, mixing thoroughly until combined. Add the Italian seasoning, salt, and pepper. Mix well to combine.
Add tomatoes - Stir in the tomatoes, sugar, Worcestershire sauce, water, and return the cooked ground beef back to the pot. Mix well to combine. Bring sauce to a low boil, then reduce heat to medium-low, cover, and allow the sauce to simmer for at least 20 minutes.
Blanch your bell peppers - Working in batches, add the stemmed and seeded bell peppers to the pot filled with boiling water. Allow peppers to cook for 2 minutes max. Use tongs and immediately transfer to an ice water bath to stop any additional cooking. Repeat until all bell peppers have been boiled.
Transfer peppers to prepared baking pans - Transfer your blanched peppers to your prepared baking pans (6 peppers fit comfortably in one pan, so plan to for two baking pans or cook your peppers in batches.
Combine sauce with rice and cheese - After the sauce has simmered for approximately 20 minutes, remove from heat and add the cooked rice, 1 cup of shredded mozzarella cheese, and 1 cup of shredded parmesan cheese. Mix well to combine. Season with additional salt and pepper, to taste.
Fill the peppers - Stuff each pepper with filling, top with a few leaves of fresh oregano (optional) and top with the remaining shredded mozzarella cheese. Repeat until all peppers have been stuffed.
Bake - Transfer to the oven and bake for 15-20 minutes, or until cheese is golden and melted. Remove from the oven and enjoy.