1. Arrange oven racks in upper and lower third of oven. Heat oven to 425 degrees F. Lightly brush 2 large cookie sheets with 2 teaspoons of the oil.
2. Combine turmeric, onion powder, salt and pepper in cup.
3. Quarter the potatoes lengthwise, then cut each quarter into 4 long wedges. Blot dry with paper towels. Toss potatoes with remaining 4 teaspoons oil in a large bowl. Sprinkle potatoes with half the spice mixture, turning potatoes gently with a rubber spatula. Toss potatoes again with remaining spices until thoroughly coated on all sides. Divide and spread potatoes evenly on the 2 large baking sheets. Bake 24 to 28 minutes, switching pans halfway through, until potatoes are golden and crisp. Makes 4 servings.