Zucchini Gratin
["olive oil cooking spray", "4 medium-sized zucchini, ends trimmed and cut crosswise into 1/4-inch thick slices", "salt to taste", "1/4 tsp. freshly ground black pepper", "1 Tbsp. chopped fresh thyme leaves or 1 tsp. dried oregano, marjoram or basil", "2 Tbsp. extra virgin olive oil"]
["Preheat oven to 350\u00b0.", "Lightly spray bottom and sides of round, ovenproof baking dish (approximately 9-inch wide and 1-inch deep; a pie dish may be used)."]
["olive oil cooking spray", "zucchini", "salt", "freshly ground black pepper", "thyme", "extra virgin olive oil"]