Whisk eggs, 2 tablespoons Parmesan cheese, basil, oregano, Dijon mustard, pepper, and salt in medium bowl to blend.
Heat oil in small ovenproof skillet over medium high heat. Add mushrooms and capers. Saute until mushrooms are brown and juices evaporate, about 6 minutes. Pour in egg mixture. Reduce heat to low. Cook without stirring until eggs are almost set, about 4 minutes. Sprinkle with remaining 2 tablespoons of cheese. Broil until top is brown and set, about 1 minute.
Cool frittata 5 m inutes. Run spatula around edges to loosen and slide out onto plate. Cut in half and serve.