Prepare the bread: In a large bowl, combine the cubed bread, melted butter, olive oil, onion powder, garlic powder, salt, and black pepper. Toss to coat the bread evenly.
4 cups cubed bread, 2 tablespoons unsalted butter, 2 tablespoons olive oil, 1 teaspoon onion powder, 1 teaspoon garlic powder, ½ teaspoon kosher salt, ½ teaspoon freshly ground black pepper
Roast the croutons: Spread on a baking sheet and toast in the preheated oven until the croutons are lightly browned and dry, 12-18 minutes. Remove and set aside to cool.