Preheat the Oven: Preheat your oven to 350°F (175°C).
Cook the Rice: If you’re using uncooked rice, prepare it according to package instructions. You’ll need about 2 cups of cooked rice for the casserole.
Brown the Ground Beef: In a large skillet over medium heat, add the ground beef. Cook until browned, breaking it apart with a spatula. Drain any excess fat.
Sauté Vegetables: Add the diced onion and bell pepper to the skillet with the beef. Cook for about 5 minutes until the vegetables are softened.
Combine Ingredients: In a mixing bowl, combine the cooked rice, browned beef and vegetables, diced tomatoes, cream of mushroom or chicken soup (if using), garlic powder, paprika, salt, and pepper. Mix until well combined.
Transfer to Baking Dish: Pour the mixture into a greased 9x13-inch baking dish. Spread it evenly.
Add Cheese: Sprinkle the shredded cheese evenly over the top of the casserole.
Cover and Bake: Cover the baking dish with aluminum foil to prevent the casserole from drying out. Bake in the preheated oven for 25 minutes.
Uncover and Finish Baking: After 25 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Let it Rest: Once out of the oven, let the casserole sit for about 5-10 minutes before serving. This will help the flavors meld and make it easier to slice.
Garnish and Serve: Garnish with fresh parsley, if desired, and serve warm.