Preheat a grill to medium-high. On a large baking sheet, arrange the tomatoes, bell peppers, zucchini, eggplant, onion and garlic in a single layer. Brush with the olive oil and season with salt and pepper.
Transfer the vegetables to the grill and cook, turning once, until just tender and slightly charred, about 5 minutes for the tomatoes, 8 minutes for the peppers, zucchini and eggplant and 10 minutes for the onions and garlic. Return to the baking sheet and let stand until cool enough to handle.
Chop the peppers, zucchini, eggplant and onions into 1/2-inch pieces and transfer to a large bowl. Squeeze out the garlic cloves, finely chop and add to the bowl. Working over the bowl, slip off and discard the tomato skins and remove the cores, then crush the tomatoes with your hands and add to the bowl. Add the olives and vinegar, season with salt and pepper and toss.