Preheat oven to 400F. Place whole eggplant, unpeeled, on a rack in oven. Wrap the two peppers & celery stalks individually in aluminum foil & place them on rack as well. Bake for 30 minutes. Remove peppers & celery & let cool. Bake eggplant for another 15 minutes. It should be very tender & have collapsed.
When vegetables are cool enough to handle, peel eggplant, cut into several pieces & drain in a colnder for 20 minutes. Squeeze out some of the excess moisture. Chop peppers, removing stems & seeds. Leave in large pieces. Chop celery into 1/2" pieces. Dice eggplant & combnie with peppers & celery in a large bowl.
Heat a few drops of olive oil in a skillet & saute the garlic till golden. Add to hte bowl. Add remaining ingredients & mix thoroughly. Cover & let stand for 1 hour at room temperature before serving.