Preheat oven to 350 degrees. Add the oil and butter to a baking sheet and heat in the oven until the butter is melted. Add the remaining ingredients and toss to combine. Bake 10 minutes. Toss again, and bake 10 minutes more. If you want croutons that are crisp but still slightly soft, your croutons are done now! If you like them extra firm, bake them for another 5 minutes. Keep in mind they will get crispier as they cool.Allow to cool to room temperature. Store in an airtight container. Homemade croutons will keep anywhere from 1 to 6 weeks depending on how crisp they are.