Preheat oven to 350°. Cook and drain sausage and onions. Mix all ingredients reserving most of the cheese for the top. Pour into a well sprayed 11 x 17" pan or two smaller pans. Top with remaining cheese. Bake in the middle of the oven for about 40 minutes, center should be just set. Cut into squares and serve warm.
Special Note: This can be made and baked in large muffin tins and frozen for 'on the go' breakfasts.