Preheat oven to 450°.
Coat cut sides of bread with cooking spray; place bread, cut sides up, on a baking sheet. Bake at 450° for 3 to 5 minutes or until lightly browned.
Spread 1/4 cup marinara sauce on each bread quarter; top each with 1/4 cup cheese. Bake at 450° for 5 minutes or until cheese melts.