Preheat the oven to 375°. On a large baking sheet, toss the bread cubes with the olive oil and season with salt and pepper. Bake the bread cubes for 6 minutes, then toss with the thyme leaves. Bake for about 6 minutes longer, until the croutons are golden and crisp.
The croutons can be stored in an airtight container for up to 1 week. Recrisp in a warm oven before serving.