Green Chili Casserole

Preheat oven to 325 degrees F (165 degrees C). Grease a medium sized casserole dish. In a medium skillet over medium heat, cook the ground beef until evenly browned; drain fat. Place half of the tortillas on the bottom of the prepared casserole dish and spread with half of the onion, cheese, ground beef and chiles. Layer with the remaining tortillas, onion, half of the remaining cheese, ground beef and chiles. In a medium bowl, dilute the soup with milk and pour over the top of the casserole. Bake in the preheated oven for 30 minutes. Sprinkle with the remaining cheese and bake for another 5 to 10 minutes, or until the cheese has melted.