Lightly spray the inside of your slow cooker with cooking spray for easier cleanup. Add the browned and drained ground beef, chopped bell peppers, rinsed uncooked white rice, tomato pasta sauce, and water to the slow cooker. Stir everything together until well combined.
Season the mixture with salt, black pepper, and Italian seasoning or dried oregano if using. Stir again to distribute the seasoning evenly throughout the soup.
Cover and cook on LOW for 6–7 hours or on HIGH for 3–4 hours, until the rice is tender and the bell peppers are soft. Stir once or twice during the last hour of cooking if you are home, to keep the rice from sticking around the edges.
Taste the soup and adjust the seasoning with a little more salt and pepper if needed. If the soup is thicker than you like, stir in an extra 1/2 to 1 cup of hot water or broth until it reaches your preferred consistency.
