If you don't have cooked rice, make some (this step can be done ahead of time if you want). I typically just make 1/2 cup uncooked rice which ends up making a bit more than you need for this recipe, and then I save the rest for another time.
Preheat your oven to 400F and move the rack to the middle position. Meanwhile, prep your ingredients. Cut the tops off the peppers as if you were carving a pumpkin (do it as evenly as possible so the filling doesn't fall out). Remove any seeds/membrane. Chop up the usable stuff from the pepper tops (you'll add it to the filling).
Place the peppers cut-side up in a baking dish (I used a 9x13). Add one cup of water to the bottom of the dish (the peppers will steam and cook faster).
Add the oil, onion, and chopped up pepper tops to a skillet. Sauté over medium-high heat for 5 minutes.
Add the ground beef to the skillet. Cook it, breaking up the meat as you go along, until it's browned and cooked through (about 8 minutes). Spoon out most of the fat/liquid.
Stir in the garlic, followed by the crushed tomatoes, Worcestershire sauce, and Italian seasoning. Let it warm through and then take the pan off the heat.
Stir in the cooked rice and 1/2 of the cheese. Season the mixture with salt & pepper as needed (give it a taste). I was generous with both the salt & pepper. Spoon the mixture into the peppers.
Cover the baking dish tightly with foil. Place it in the oven and bake for 40 minutes.
Take the dish out of the oven. The peppers should be still a little bit firm to the touch (you don't want them to go limp and fall apart, but if they feel too firm, cook them for longer). Sprinkle the rest of the cheese over top. Return the peppers to the oven (uncovered) for another 5-10 minutes or until the cheese is melted. You can broil at the end for a few minutes if you want the cheese to be a bit browned.