In a large bowl, whisk together the eggs, milk, salt and pepper.
Heat the olive oil in a 10-inch non-stick ovenproof skillet over medium high heat. Sauté the mushrooms for 5-7 minutes until they turn brown. Stir in the roasted tomatoes and parsley and reduce the heat to low.
Pour in the egg mixture. Allow the eggs start to set at the edges, about 2-4 minutes. Transfer the skillet to the oven and bake for 8-10 minutes until just set in the middle.
Sprinkle with parsley before serving.
Notes
Store leftover frittata in the refrigerator and serve cold.