Place the corn on a microwave-safe plate. Cover with waxed paper. Microwave on high for 2 minutes., On two metal or soaked wooden skewers, alternately thread the corn, zucchini, onion and tomatoes. Lightly coat vegetables with cooking spray. In a small bowl, combine the seasonings; sprinkle over vegetables., Using long-handled tongs, moisten a paper towel with cooking oil and lightly coat the grill rack. Grill vegetables, covered, over medium heat or broil 4 in. from the heat for 6-12 minutes or until vegetables are tender, turning frequently.