Preheat the oven to 400°F. In a large bowl, mix the onion powder, paprika, thyme, crushed garlic, rosemary, parmesan cheese, and salt and pepper together.
Cut the potatoes into wedges by slicing them in half lengthways and then into thirds lengthways too.
Toss the sliced potatoes into the oil and spices to coat all over.
Arrange the wedges into the baking dish skin side down and pop into the oven to bake for 30-35 minutes.