Vegetables can be difficult to get right on the grill. But if done correctly, they will bring healthy and delicious dishes to your cookout. According to Cook’s Illustrated, asparagus should be grilled five to seven minutes with a single turn. Corn can be grilled for eight to 10 minutes with one layer of husk on, and eggplant and zucchini take about the same time when sliced into rounds or planks. Portobello mushrooms should be brushed with oil and grilled eight to ten minutes; skewered onions, 10 to 12 minutes. Pretreat your grates by brushing them with olive oil for the best results, and enjoy!