Break the bread into small pieces and put in a large mixing bowl. Add the chopped onions, scallions, lettuce, parsley, cucumber, tomatoes, and mint. Mix well, then leave the bread to absorb the juices, about 10 minutes.
Now make a dressing with the lemon juice, olive oil and garlic. Season with salt and black pepper and pour over the salad mixture. Toss well and chill before serving. Serves 4-6.