In a 13x9x2-inch baking pan arrange potatoes, carrots, parsnip, and, if desired, red onion. In a small bowl combine oil, garlic, mixed herbs, salt, and pepper. Drizzle oil mixture over vegetables; toss to coat. Cover with foil.
Bake in a 425 degree F oven for 30 minutes. Remove foil; stir vegetables. Bake, uncovered, for 5 to 10 minutes more or until vegetables are tender. Makes 6 servings.