Heat a large nonstick skillet over medium-high heat. Lightly coat the sausages with cooking spray. Add the sausages to pan; cook 5 minutes or until browned, turning once. Chop sausages.
Arrange 6 bread slices in bottom of a 13 x 9-inch baking dish coated with cooking spray. Arrange sausage and 1/2 cup cheddar cheese over bread. Top with remaining bread slices. Combine fat-free milk, salt, pepper, and egg substitute, stirring with a whisk. Pour over bread mixture. Let stand for 30 minutes.
Preheat oven to 400°.
Sprinkle remaining 1/4 cup cheese over bread mixture. Bake at 400° for 30 minutes or until puffed and browned. Let stand 5 minutes before serving.