Slice eggplants into 3/4-in. slices. Place on a cooling rack over a sheet pan and sprinkle lightly salt, turn over and do the other side. Let stand 30 minutes.
Preheat your grill to achieve a medium high heat.
While the eggplant sits, place the pepper and onion slice on a plate. Sprinkle with salt, pepper and garlic powered. Lightly brush with olive oil to coat.
When the eggplants are done, blot them dry with a paper towel. Sprinkle with salt, pepper, and garlic powder then lightly brush with olive oil to coat.
Moving to the grill, place the pepper (skin side down) and onion, and eggplant on the grill surface.
Grill, uncovered, over medium-high heat for about 4 - 5 minutes per side, slightly charred, turning each piece over just once.
While vegetables are gilling, brush both sides of the pita breads with remaining olive oil.
Transfer grilled vegetable into a work bowl and then onto a cutting board. Roughly chopped them together to create a medley of vegetables. Add the chopped tomatoes and kalamata olives and toss together.
Turn the heat down to medium low and place the pitas on the grill
Grill one side only, covered, over medium-low heat for about 2 minutes or until bottoms are lightly browned and beginning to char. Remove from grill.
Layer grilled sides of pitas with grilled vegetables, tomato, cheese and olives.
Return to grill. Turn the grill off, and close the lid.
Cook, covered, for about 4 minutes, until tomatoes are gently warmed
Remove from grill, and sprinkle with crumbled feta cheese and oregano