Start a charcoal or gas grill; fire should be medium-high and rack about 4 inches from heat source.
When fire is ready, rub tuna lightly with olive oil, then sprinkle it with salt and pepper. Put it on grill and grill about 3 to 4 minutes a side for medium-rare, more or less according to your desired degree of doneness.
Meanwhile, combine olives, herbs, garlic if you are using it and just enough oil to moisten and bind the mixture, no more than a tablespoon.
When tuna is done, spread a portion of herb mixture on 1 side of each steak and serve with lemon wedges.
Wine suggestion for this recipe:
Recipe courtesy of Mark Bittman