Preheat oven to 375 deg. Oil 2-quart gratin or baking dish. Heat the olive oil in large, nonstick skillet over medium heat and add the onion. Cook, stirring often, until it begins to soften, about 3 min. Add the red pepper and cook stirring often, until the onions and peppers are tender, about 5 min. Add the garlic and the zucchini, stir together and add pinch of salt and black pepper. Cook, stirring often, until the zucchini is just beginning to look bright green and some of the slices are translucent. Stir in half the corn and cook for 1-2 min. Remove from heat and scrape into a large bowl.