Preheat oven to 425 degrees. Place foil on cookie sheet.
In a medium bowl mix eggplant, zucchini, tomatoes, onion, 2 tablespoons olive oil, balsamic vinegar, garlic, basil, salt and black pepper together. Spread across cookie sheet so it's even, and roast for about 20 minutes.
Prepare bread by cutting 12 1/2 inch slices, and spray each with non stick cooking spray. You can either toast in toaster oven, or place in oven once eggplant is finished for about 10 minutes until golden brown.
Once finished, spread eggplant mixture on toasts immediately and sprinkle feta on top.