Preheat broiler. In a 10-inch broiler proof skillet, heat 2 tablespoons of the oil over medium heat. Add onion and garlic; cook just until onion is tender.
Meanwhile, in a large bowl, combine eggs and half-and-half; beat with a rotary beater. Stir in feta cheese, roasted sweet peppers, olives, basil, and black pepper. Pour over onion mixture in skillet. Cook over medium heat. As egg mixture sets, run a spatula around the edge of the skillet, lifting egg mixture to allow the uncooked portion to flow underneath. Continue cooking and lifting edge until egg mixture is almost set (surface will be moist). Reduce heat as necessary to prevent overcooking.
In a small bowl, combine crushed croutons, Parmesan cheese, and the remaining 1 tablespoon oil; sprinkle mixture over frittata.
Place skillet under broiler 4 to 5 inches from the heat. Broil for 1 to 2 minutes or just until the top is set. Cut into wedges to serve. Makes 6 servings.