Pierce the eggplant a few times with the tip of a paring knife or fork. Cook eggplant on preheated grill, turning often, until the skin is charred and the eggplant is tender, about 15 minutes. Set aside until cool enough to handle.
Remove the skin from the eggplant and dice the pulp. Place into a mixing bowl, and add tomato, onion, parsley, olive oil, vinegar, and feta cheese; mix well. Refrigerate for one hour, and season to taste with salt before serving.
