Beefy Au Gratin Potatoes

Beefy Au Gratin Potatoes
1 package (5-1/4 ounces) au gratin potatoes or cheddar and bacon potatoes
1 can (15-1/4 ounces) whole kernel corn, drained
1 can (10-3/4 ounces) condensed cream of potato soup, undiluted
1 cup water
1 can (4 ounces) chopped green chilies, drained
1 can (4 ounces) mushroom stems and pieces, drained
1 jar (4 ounces) diced pimientos, drained
1 pound ground beef
1 medium onion, chopped
Set potato sauce mix aside. Place potatoes in a 3-qt. slow cooker; top with corn. In a bowl, combine soup, water, chilies, mushrooms, pimientos and reserved sauce mix; mix well. Pour a third of the mixture over corn. In a skillet, cook beef and onion over medium heat until the meat is no longer pink; drain. Transfer to slow cooker. Top with remaining sauce mixture. Do not stir. Cover and cook on low for 4 hours or until potatoes are tender.