Preheat oven to 400 degrees. Grease a 9" pie plate or casserole dish. In a medium skillet, sauté onion, chiles, and sausage until sausage is cooked through and no longer pink. Drain. Combine sausage mixture with hash brown potatoes and 1 cup shredded cheese. Pour into casserole dish.

Whisk together eggs, milk, Bisquick, and pepper. Pour over sausage mixture.

Bake uncovered for 30 - 35 minutes or until knife inserted in center comes out clean. Sprinkle 1/2 cup shredded cheese on top and bake an additional 2-3 minutes until cheese has melted. Let stand for 5 minutes before serving.