Preheat oven to 500°F. Line a large, rimmed baking sheet with foil. Arrange bread, cut side up, on baking sheet.
Melt butter in a small pan over medium heat. Add garlic, salt, pepper and oregano; cook, stirring once or twice, until garlic is fragrant, 1 to 2 minutes.
Use a pastry brush to spread garlic butter evenly over bread. Sprinkle evenly with cheese. Bake until bread is golden, 8 to 10 minutes. Cut loaf halves into thick slices and serve.