In a small bowl, combine the eggs, salt, pepper, parsley and all but 1 tablespoon of the mozzarella. Whisk to combine and set aside.
In a small skillet or cast iron pan, heat the oil over medium to medium high heat. Add then potatoes and cook. Put a lid over the pan to hold in the heat and cook the potatoes, stirring occasionally to prevent burning, 3-5 minutes. Add the onions and cook for an additional 3-4 minutes or until potatoes and onions are tender. Stir in the canadian bacon and sun-dried tomatoes and cook for about a minute until warmed through.
Spread the ingredients in the skillet into an even layer. Pour the egg mixture into the skillet and top with mozzarella cheese. Cook on top of the stove until the bottom of the frittata is set but the eggs on top are still uncooked, about 2 minutes. Transfer the skillet to the oven and bake for 3-5 minutes or until the top of the frittata is set. Turn the oven to broil and heat for 1-2 minutes, until the top of the frittata is lightly golden. Remove from oven and serve.