With the rack in the middle position, preheat the oven to 425 °F (210 °C).
In a 9-inch (23 cm) cast iron skillet over medium heat, soften the bell peppers, onion and garlic in the oil for about 5 minutes. Add the sausages so that they touch the bottom of the skillet. Bake for 20 minutes. Remove for the oven, turn the sausages grilled side up.
Meanwhile, in bowl, combine the eggs, half the green onions and half the cheese. Season with salt and pepper. Pour into the skillet through the sausage and vegetables so that they are visible on the surface. Bake for about 15 minutes or until the eggs are cooked.
In a bowl, combine the remaining green onions and cheese with the parsley.
Right out of the oven, garnish the frittata with the green onion mixture. Serve with toasted crusty bread if desired.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.