Preheat the grill to medium-high heat.
Brush the eggplant slices with olive oil and sprinkle with salt and pepper. Place the eggplant slices on the grill and cook for about 5 minutes per side or until golden brown.
In a large bowl, combine the grilled eggplant, bell peppers, red onion, tomatoes, and feta cheese.
In a small bowl, whisk together the olive oil, balsamic vinegar, garlic powder, and onion powder. Pour the dressing over the salad and toss to combine.
Serve the salad warm or cold.