Peel and rinse potatoes, cut into small wedges, then dry. Place in a large bowl, add zucchini also cut into small wedges, and sliced onion. Toss with olive oil, salt, oregano, rosemary, and garlic. Mix well.
Transfer to large baking sheet. Sprinkle with additional oregano and salt. Bake in a pre-heated oven for approximately 1 hour. Serve immediately.