Instead of using baby-cut carrots, peel full-size carrots and cut into 2x1/4-inch strips. You can also use yellow or white onions in place of the red variety.
Buy cauliflower that is firm and creamy white with compact flowerets. The size of the head doesn’t affect the quality. Avoid heads with any sign of mold or wilted leaves. To store it, wrap cauliflower tightly and refrigerate for 3 to 5 days.
You can assemble this packet up to eight hours ahead of time. Keep it refrigerated until you’re ready to grill.