Place the peppers, skin side up, on a foil-lined grill rack and grill under a preheated moderate grill for 10–15 minutes or until the skins are blackened.
Meanwhile, quarter the tomatoes and scoop out the pulp, placing it in a sieve over a bowl to catch the juices. Set the tomato quarters aside. Press the pulp with the back of a spoon to extract as much juice as possible. Beat the oil, vinegar, garlic and salt and pepper into the tomato juice.
When cool enough to handle, peel the skins from the peppers and discard. Roughly slice the peppers and place in a bowl with the tomato quarters, bread, olives and basil. Add the dressing and toss the ingredients together. Chill until required.