Start by heating a large skillet over medium heat. Add your ground beef and Italian sausage. Cook until the meat is browned and no longer pink, breaking it up with a spatula as you go. Toss in your diced onion, bell peppers, and minced garlic. Let everything cook together for about 5 minutes until the veggies are soft and fragrant. Drain any excess fat.
Now it’s time to build your sauce. Stir in the diced tomatoes (with their juices), tomato sauce, beef broth, uncooked rice, and all your seasonings—Italian herbs, paprika, and red pepper flakes if you like heat. Stir well and bring the mixture to a boil. Once boiling, lower the heat, cover it, and let it simmer for 20-25 minutes, giving it a stir every few minutes. The rice should cook through and absorb those delicious flavors.
Preheat your oven to 375°F (190°C). Grab a 9x13-inch baking dish and lightly grease it. Transfer your meat and rice mixture into the dish and spread it out evenly.
Sprinkle that generous layer of shredded mozzarella cheese over the top. Pop it into the oven and bake for about 15–20 minutes. You’ll know it’s ready when the cheese is melted and bubbly with golden spots.
Once out of the oven, let the casserole sit for about 5 minutes. This helps it set a bit. Sprinkle some chopped parsley over the top for a fresh finish.