Preheat oven to 350°
Lightly grease a 2-quart casserole dish, set aside.
In a medium bowl, combine leeks, zucchini, yellow or pattypan squash.
Toss with olive oil. Sprinkle with garlic and herb seasoning.
Transfer vegetables to prepared casserole dish.
In a small bowl, combine bread crumbs, Parmesan cheese, garlic and herb seasoning and melted butter, set aside.
In a medium bowl, combine soup, cheese and parsley.
Spoon over vegetables in prepared pan.
Sprinkle with breadcrumb mixture.
Bake casserole, covered for 20 to 25 minutes.
Remove foil, bake an additional 20 to 25 minutes or until vegetables are tender and casserole is heated through.
Let dish stand 5 to 10 minutes before serving.