Preheat the oven to 325°F. Toss together the bread, oil, cheese, garlic, oregano, salt, and pepper in a bowl, coating evenly.
Spread on a baking sheet in a single layer. Bake, turning with a spatula every 10 minutes, until browned and crisp, 20 to 30 minutes.
Cool on the baking sheet for 10 minutes.
Store the cooled croutons in an airtight container for up to 2 weeks.