1 day ahead: Cook carrots, zucchini, and pattypan squash in boiling salted water 2 to 3 minutes or until crisp-tender; drain. (If using zucchini or crookneck squash, slice 1/4 inch thick; omit precooking.) Plunge vegetables into ice water; drain and pat dry.
15 minutes ahead: Place skewers in water to cover; let soak 10 minutes.
Thread vegetables onto skewers. Brush with olive oil; sprinkle lightly with Grill Mix. Grill vegetables, covered with grill lid, over medium-high heat (350 degrees F to 400 degrees F) 4 to 5 minutes on each side, or to desired degree of doneness. Serve warm with Roasted Garlic-Saffron-Pinot Grigio Whipped Butter.