Heat up your barbecue. Toss the potatoes in olive oil, salt and pepper and throw in a barbecue basket (roasting in the oven is also an option). Cook over a medium heat on the barbecue. Toss them every 5 minutes so they are cooked on all sides. Cook for ~10-12 minutes. You can do the rest of the veggies when the potatoes are halfway done.
Toss the zucchini, onions and peppers in olive oil, salt and pepper. Grill on a medium heat on the barbecue. When coloured on one side, flip and cook on the other side. Keep a close eye on the veggies as they can overcook quickly. When done, remove from the barbecue and chop into bite size pieces. Add the veggies to the potatoes and add dressing as necessary. You may not need all the dressing. Top with cilantro leaves. Serve warm, room temperature or chilled, although I prefer slightly warm.