Preheat a campfire grill grate or barbecue to medium-high heat.
Toss the zucchini, peppers, onion and garlic with olive oil, mustard, tarragon, salt and pepper.
Divide the vegetables among 4 large sheets of heavy-duty foil, lined with parchment paper. Place one sausage on each pile of vegetables.
Pour the wine evenly over each packet.
Fold tightly to seal.
Cook for 18–22 minutes, turning once, until the sausages reach an internal temperature of 71°C (160°F) and the vegetables are tender.
Open carefully and spoon the cooking juices over top before serving.
