MIX oil, vinegar, juice and dressing mix in cruet or small bowl as directed on package. Reserve 1/4 cup dressing; refrigerate until ready to use.
POUR remaining dressing over vegetables in shallow glass dish; cover. Refrigerate 1 hour to marinate, stirring after 30 min. Drain vegetables; discard marinade.
HEAT greased grill to medium-high heat. Grill vegetables 8 to 10 min. or until crisp-tender, turning and brushing occasionally with reserved dressing.