To get more mileage out of this recipe, leave the vegetable mixture to marinate in the refrigerator and use it for another dish later in the week.
Spread bread on pan to dry out for a couple hours or overnight.
Place pepper, cucumber, tomato, and onion in a bowl. Mix together olive oil, red-wine vinegar, sugar, and salt, and pour over vegetables; toss to coat. Add the bread and toss to combine. Allow the bread to sit for a bit to soak up the dressing. Crumble feta cheese on top. Cover and refrigerate up to overnight.