Arrange bread cubes in a single layer on large baking sheets. Let stand 8 hours to dry.
Spread half of bread cubes in a lightly greased 13 x 9 baking dish. Sprinkle prosciutto and next 3 ingredients evenly over bread cubes. Arrange remaining bread cubes evenly over Parmesan. Top with tomatoes, olives, and mozzarella cheese.
Whisk together eggs and remaining 5 ingredients. Pour egg mixture evenly over bread cubes, pressing down cubes gently to absorb liquid; cover and chill 8 hours.
Bake, uncovered, at 325° for 55 minutes or until set and top is browned. Let stand 10 minutes before serving.