Preheat oven to 400 degree F. Combine the 2 tablespoons olive oil and garlic. Brush both sides of bread slices with olive oil mixture. Place on a baking sheet and bake for 4 minutes. Turn and bake for 4 to 5 minutes more or until toasted. Set aside.
In a 10-inch skillet bring water and spaghetti sauce to boiling; stir in macaroni (see photo, above right). Return to boiling; reduce heat. Cover and simmer 12 minutes, stirring pasta occasionally.
Meanwhile, place vegetables in a colander; run cool water over the vegetables to thaw. Press with rubber spatula to remove excess liquid. Transfer vegetables to a large bowl. Add the 2 teaspoons olive oil, 1/4 teaspoon salt, and 1/8 teaspoon pepper; toss mixture gently to coat. Set aside.
In a small bowl stir together ricotta cheese, milk, dried oregano, and 1/4 teaspoon pepper. Stir in the 1/2 cup mozzarella cheese and the Parmesan cheese.
Spoon cheese mixture into center of skillet over pasta mixture, spreading slightly to make a 4- or 5-inch circle. Spoon vegetables evenly around edge of skillet over pasta mixture (do not cover cheese in center). Simmer, covered, 10 minutes or until vegetables are crisp-tender.
Just before serving, sprinkle the 1/4 cup mozzarella over vegetables and cheese mixture, and arrange bread slices on top of cheese mixture. If desired, garnish with fresh oregano sprigs. Makes 6 servings.