Heat a large skillet over medium-high heat; cook and stir beef and onion until beef is browned, about 5 minutes. Transfer beef and onion to a slow cooker. Add sweet corn, cream-style corn, potatoes, and parsley. Pour enough water into the slow cooker to fill completely.
Cover and cook corn mixture in slow cook on Low until potatoes are very tender, about 6 hours. Season with salt and pepper.