01 - Heat a large skillet over medium heat. Add the ground beef and diced onion, cooking until the meat is no longer pink. Break up any large chunks with a spoon. Drain excess fat from the skillet.
02 - Transfer the beef and onion mixture to the slow cooker. Spread evenly across the bottom to create a solid base layer.
03 - Arrange the diced potatoes, kidney beans, and corn in even layers over the beef mixture. Pour the diced tomatoes with their juices evenly across the top.
04 - In a small bowl, whisk together the condensed cream of mushroom soup, beef broth, smoked paprika, garlic powder, dried oregano, black pepper, and salt until smooth and well combined.
05 - Pour the seasoned soup mixture evenly over all the layered ingredients in the slow cooker. Cover with the lid and cook on LOW setting for 6 hours, or until the potatoes are fork-tender.
06 - During the final 15 minutes of cooking, sprinkle the shredded cheddar cheese over the top of the casserole. Cover again and allow the cheese to melt completely.
07 - Spoon the hot casserole into bowls and serve immediately. Garnish with fresh chopped parsley or sliced green onions if desired.