Preheat the oven to 350 degrees. Clean the bell peppers by slicing off the tops and with a pairing knife, cutting the white ribs and removing any excess seeds. This will hollow out your pepper and get it ready for stuffing.
In a large bowl, add your ground meat, breadcrumbs, parmesan cheese, 1/2 cup of the rice and about 1/4 cup of the marinara sauce. Mix to combine, but be careful not to over mix as you can make the mixture tough. Form into 4 large "meatballs" to add to the peppers.
To assemble, scoop 1/4-1/2 cups of the rice into the bottom of the pepper depending on how large your pepper is. You do not want too much rice as you are going to add the meat on top. So, it should just be the bottom about 1/3. Then scoop about 1-2 tablespoons of the marinara over the rice. Top the marinara with the meat mixture.
Place the peppers in a baking sheet that has been lined with a layer of marinara sauce. This will be the bed for the peppers and help them steam on the outside and in part flavor on the inside. Place the peppers on top of the layer of marinara sauce. Top the peppers with another ladle or two of the marinara sauce and then with the shredded mozzarella cheese. Cover the whole thing with plastic wrap and then aluminum foil.
Bake for 45 minutes-1 hour or until a pairing knife can be inserted into the pepper and come out very easily with no resistance. Also, the cheese should be completely melted. Uncover and cook for another 10-15 minutes or until the cheese on top is golden and bubbly.
Let the peppers cool slightly and then serve them hot with a nice little salad or side of pasta. ENJOY!