1. In a large bowl, combine potatoes, onion, garlic, oil and thyme; toss well to coat. Pour vegetables in to a shallow roasting pan or jelly roll pan.
2. Bake in a 425F oven, turning frequently, for 40-45 minutes or until vegetables are soft and golden brown.
3. Add pecans during the last 10 minutes of baking. Drizzle with vinegar. Season with salt and pepper.