In a large covered pot soak the beans in 8 cups water overnight; rinse and drain. In the same pot, heat 2 tablespoons olive oil over medium-high heat. Add the onion, reduce heat, and saute until translucent, but not brown, about 8 minutes. Add the garlic and cook for 1 minute more. Add the beans, 8 cups fresh water, and 2 teaspoons salt. Bring to a boil, reduce heat, and simmer, uncovered, for 1 to 1-1/2 hours or until beans are tender, stirring occasionally. If the liquid level gets below the beans, add additional water. Remove from heat. Stir in oregano. Remove 2 cups beans with a slotted spoon; keep warm. Store the remaining beans in a covered container in the refrigerator or freezer in their cooking liquid for Pasta and White Bean Stew later in the week.
Preheat oven to 400 degree F. Line a shallow baking pan with parchment paper. Season the fish with salt and pepper and sprinkle with lemon peel. Place the fillets in the prepared pan. In a medium bowl mix the tomatoes, olives, 2 tablespoons oregano, and 1 tablespoon olive oil. Spoon tomato mixture over fish.
Roast, uncovered, for 12 to 15 minutes or until fish flakes easily when tested with a fork. Serve fish and tomato mixture with beans and lemon wedges. Makes 4 servings.