My Spinach Feta Egg Muffins are the perfect simple, easy, prep-ahead breakfast that will make your mornings a breeze. Simply prepare a batch (or two, or three) of these ahead of time, stick them in the freezer, and pop them out and reheat them anytime that you need a healthy and delicious breakfast treat. Plus, this recipe also happens to be naturally gluten-free, grain-free, and vegetarian-friendly!