Preheat oven to 350° F . Coat an 8x8 inch baking dish with olive oil or cooking spray. The key is that you have a well greased pan.
Heat the olive oil in a skillet over medium-high heat. Place all veggies in the skillet. Season with salt, pepper and garlic powder. Cook until tender.
Transfer to the prepared baking dish. In a glass bowl, whisk eggs and mustard together and transfer to baking dish with the veggies.
Bake 25 minutes in the preheated oven, or until eggs are set in the middle. Cooking time will depend on your oven, but start checking around 25 minutes. If you will be reheating throughout the week, you do not want to over cook the eggs or they will dry out. Cut with a spatula and enjoy for a few days to come!