Heat a large skillet over medium heat. Add 1 tablespoon oil if your beef is very lean.

Brown the ground beef, breaking it into small pieces.

When the beef is halfway done, add the chopped onion. Cook for 4–5 minutes until the onion softens. Stir in garlic and cook for 1 minute until fragrant.

Drain excess grease from the skillet. Season the meat with salt, pepper, Italian seasoning, and paprika. Stir in Worcestershire sauce if using.

Lightly grease a 4- to 6-quart slow cooker. Spread the rinsed, uncooked rice in an even layer on the bottom.

Pour the undrained diced tomatoes, cream of mushroom soup, tomato soup, and beef broth over the rice. Stir gently so the rice is mostly covered by liquid.

Add the cooked beef and onion mix on top. Sprinkle frozen mixed vegetables over the beef if using. Stir once to distribute everything evenly.

Cover and cook on LOW for 4–5 hours or on HIGH for 2–3 hours, until the rice is tender and most liquid is absorbed. Avoid lifting the lid while it cooks.

Taste and adjust salt and pepper. If using cheese, sprinkle shredded cheddar over the hot casserole, cover, and let sit for 10 minutes on WARM or LOW so the cheese melts.

Stir gently to combine, or scoop out into bowls with a cheesy top. Serve hot.