Preheat the oven to 375 degrees F.
Using 1 teaspoon of the oil, grease a large oven dish.
In a medium bowl, combine the olives, parsley, and garlic. If using a snapper, stuff the cleaned fish with half the mixture, place the fish in the dish, and sprinkle the remaining mixture over the top of the fish. If using steaks, place them in the oven dish and sprinkle with all of the mixture. Season with salt and pepper and drizzle with lemon juice and remaining olive oil.
Cook in oven 30 minutes, basting every 10 minutes with pan juices. Serve immediately, garnished with lemon zest and parsley.