1. Preheat grill to 350 degree.
2. Grease a 2 quart baking dish. Place the 2/3 hash brown potatoes in the bottom of the baking dish.
3. Heat a skillet over medium heat and cook and stir the sausage and onion until the sausage is crumbly, evenly browned, and no longer pink; drain.
4. Whisk together the eggs, milk, spices and pour over the potatoes. Layer with half the Cheddar cheese, the sausage mixture, the last 1/3 of potatoes and the remaining cheese. Cover with aluminum foil.
5. Bake for 1 hour. Remove cover; return casserole to the grill and bake until a knife inserted into the center comes out clean, about 10 minutes. Let stand for 5 minutes before serving.
Note: You can also add any other types of sausage. Occasionally, we smoke a link of andouille and add quartered bits in with the regular breakfast sausage. For a triple pork option, add cooked bacon bits to the topping during the last ten minutes.