Preheat the oven to 375°F (190°C).
In a large skillet over medium-high heat, cook the ground beef until browned, breaking it apart with a spoon. Drain excess fat.
Add the diced onion and minced garlic to the skillet with the beef. Cook for 3-4 minutes until the onion is softened.
Stir in the diced bell peppers and cook for an additional 3 minutes until slightly tender.
Add the uncooked rice, diced tomatoes with their juice, tomato sauce, beef broth, Italian seasoning, salt, and black pepper to the skillet. Stir well to combine.
Bring the mixture to a simmer, then remove from heat.
Transfer the mixture to a 9×13 inch casserole dish and spread evenly.
Cover the casserole dish tightly with aluminum foil and bake in the preheated oven for 35 minutes.
Remove the foil and sprinkle the shredded cheddar cheese evenly over the top.
Return the casserole to the oven and bake uncovered for an additional 5 minutes, or until the cheese is melted and bubbly.
Remove from oven and let the casserole rest for 5 minutes before serving.