PREHEAT oven to 400° F. Line baking sheet with foil.
PLACE zucchini, bell peppers and onion in single layer on prepared baking sheet. Drizzle with oil and sprinkle with 1/4 teaspoon black pepper and 1/4 teaspoon thyme; toss lightly to coat.
BAKE for 20 to 25 minutes or until vegetables are just tender. Transfer to 2-quart serving dish.
MEANWHILE, HEAT evaporated milk, wine, cornstarch, remaining 1/4 teaspoon black pepper and remaining 1/4 teaspoon thyme, salt and onion powder in small saucepan over medium-high heat. Bring just to a boil; reduce heat to medium. Cook, stirring constantly, for 2 to 3 minutes or until slightly thickened. Stir in cheese, 1/2 cup at a time, allowing each addition to be melted before adding more cheese. Remove from heat.
POUR cheese sauce over vegetables; toss lightly to coat. Season with additional salt and black pepper, if desired. Serve immediately.
• Large diameter zucchini or yellow summer squash may be cut in half or quarters