Prepare and refrigerate this side dish up to two days ahead; let it come to room temperature before serving. It's good with grilled chicken, lamb, or fish.
Sprinkle cut sides of eggplant with 3/4 teaspoon salt. Let drain 1 hour. Rinse well; pat dry with paper towels.
Coat eggplant, zucchini, bell peppers, and onion with cooking spray. Place vegetables on a grill rack coated with cooking spray; grill 5 minutes on each side or until tender. Cool.
Coarsely chop vegetables, and place in a large bowl. Stir in remaining 1/4 teaspoon salt, tomatoes, and remaining ingredients, stirring until blended.