Remove the seeds from the red capsicum, and chop into 2cm strips. Cut the eggplant into rounds about 1cm thick and cut each round into 6 to 8 pieces. Peel the onion, and chop into 8 wedges. Trim the zucchini and cut into thick slices.
Heat the barbecue over high heat with olive oil. When it is very hot, put all the vegetables on the barbecue. Press down occasionally to get grill lines across them. Turn occasionally to prevent burning.
Cook for about 15 minutes, or until the vegetables are evenly browned and cooked through.
Stir broad beans, chopped tomatoes and vinegar into the vegetables. Simmer for a few minutes while the couscous is prepared.
Place couscous into a medium bowl. Add boiling vegetable stock and stir with a fork. Keep lifting the couscous occasionally to prevent it sticking. It only takes 2 to 3 minutes to become soft. Place couscous in a large bowl or serving platter, and serve the vegetables on top.