With the rack in the highest position, preheat the oven’s broiler.
On a baking sheet, combine all the ingredients. Season with salt and pepper. Bake for about 10 minutes or until the onion is tender. Remove from the oven.
Drizzle the fish fillets with the olive oil. Season with salt and pepper. Place them, skin side up, on the roasted onion and bake for about 5 minutes or until the fish is cooked. Sprinkle the fish with oregano and serve with the onions and lemon wedges.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.