Heat oven to 350° F. Spray 8- or 9-inch square baking dish with nonstick cooking spray. In 10-inch skillet cook sausage and green pepper over medium-high heat 8-10 minutes or until sausage is browned and cooked through; drain.
Place half of the Potatoes in prepared baking dish. Top with half of the sausage and 3/4 cup of shredded Wisconsin Monterey Jack cheese or shredded Cheddar cheese; repeat.
Combine eggs and milk in medium bowl; beat well with fork. Pour egg mixture evenly over layered mixture in pan. Cover with foil; bake for 45 minutes. Uncover; add chopped tomato and remaining 1/2 cup cheeses. Bake, uncovered, for an additional 10-15 minutes or until knife inserted in center comes out clean.