Spray 13X12 inch glass baking dish with nonstick cooking spray. Cook sausage in large skillet over medium-high heat until no longer pink, stirring occasionally. Remove sausage from skillet; drain on paper towels.
In large bowl, combine potatoes, onions, mushrooms, olives, 1 tbsp. basil and 2 c. of the cheese. Add sausage; mix lightly. Spoon evenly into sprayed baking dish., Sprinkle with remaining cheese.
Beat eggs in same large bowl. Add milk and ½ tsp. salt; beat well. Pour over potato mixture. Spray sheet of foil with nonstick cooking spray. Cover baking dish with foil; refrigerate 8 hours or overnight.
To serve, heat oven to 350* F. Bake, covered, for 45 minutes. Uncover; bake an additional 20-25 minutes or until center is set. Let stand 10 minutes before serving.
I sometimes use fresh mushrooms and sauté them at the end of cooking the sausage. This is a favorite at our tailgate breakfast.