In a large bowl, combine the olive oil, balsamic vinegar, garlic, salt, and pepper.
Add the olives, tomatoes, mozzarella, and basil and toss until the dressing coats all of the ingredients.
Notes
You could also use full-sized tomatoes; just cut them into 1-inch cubes. You can also cut this recipe in half; it makes a lot and serves 8, which might not be what you need.
Make-Ahead and Leftovers
You can make this salad up to a few hours ahead and let it sit at room temperature. If you want to make it a day ahead, that’s fine, too, though in a perfect world, tomatoes never see the inside of a refrigerator, and you would have to refrigerate them overnight, because of the cheese. Make sure to bring it to room temperature before serving, and if possible, slice and add the basil at the last minute.