In a large bowl, combine the bell peppers, onion, zucchini, olive oil, balsamic vinegar, garlic, mustard, oregano, basil, salt and pepper. Toss to coat evenly.
Preheat the grill to medium-high heat.
Grill the vegetables for 8-10 minutes, or until they are softened and lightly charred.
Serve warm.
Interesting Facts
Barbecuing vegetables is a great way to get the smoky flavor of the grill without the fat from meat.
Grilling vegetables helps to bring out their sweetness and makes them even more delicious.
Marinating vegetables in oil, vinegar, and spices helps to infuse them with flavor.