Southwestern Tator Tot Casserole 1 pound ground beef 1/2 cup white onion, chopped 1 pound frozen tator tots 1 (10.5 ounce) can cream of mushroom soup 1 (4 ounce) can mild green chiles Preheat oven to 350 degrees. In skillet, brown onion and beef, drain off excess fat. Place hbeef mixture into casserole dish. Top with tator tots. In bowl, combine soup and chiles. Pour over tater tots. Cover. Bake for 30 minutes.