Preheat oven to 450 degrees. Oil a baking dish. Squeeze lemon juice over fillets in baking dish. Top fillets with onion, green pepper, and tomato. Top with crumbled feta cheese. Drizzle with olive oil and season with Italian seasoning. Pour wine into baking dish. Bake fillets for 15 - 20 minutes or until fish flakes easily. Broil fish at high setting for a few minutes after baking until the cheese is browned.