Pit and thinly slice olives. Cut zucchini diagonally into 1/4-inch-thick slices and in a bowl toss with oil and salt and pepper, to taste.
Grill zucchini, in batches if necessary, on a rack set 5 to 6 inches over glowing coals 2 to 3 minutes on each side, or until lightly charred and just tender. (Alternatively, zucchini may be grilled in a hot well-seasoned heavy-ridged grill pan over moderately high heat.) Transfer zucchini to bowl and toss with olives, mint, and lemon juice. Season with salt and pepper, to taste.