How to Make It
Preheat the oven to 425°. Brush the bread on both sides with olive oil. Arrange the slices on a large baking sheet and toast in the oven until golden brown. Rub the toasts with the whole garlic clove.
In a very large bowl, combine the remaining 1/4 cup plus 2 tablespoons of olive oil with the rosemary, minced garlic and sugar. Add the corn, potatoes, squash, bell peppers and scallions to the bowl and toss well to coat. Season generously with salt and pepper.
Spread the corn and potatoes on 1 large baking sheet and the squash, bell peppers and scallions on another. Bake the squash, peppers and scallions for about 20 minutes and the corn and potatoes for about 30 minutes. The vegetables are done when they are tender and lightly browned.
Arrange 2 piles of vegetables on each toast. Top with Parmesan shavings and serve hot or at room temperature.