Preheat oven to 400 degrees F. Brush four muffin cups with olive oil and line them each with a ham slice.In a Pyrex measuring cup, whisk the eggs, salt, pepper and garlic powder.Pour the eggs evenly into the lined muffin cups. Add your filling, dividing it evenly among the cups.Bake 25-30 minutes, or until eggs are set and puffed and a toothpick inserted in the center comes out clean. Cool 5 minutes in pan, then transfer to a plate and allow to cool 5 more minutes before enjoying. If a bit of egg has spilled from the ham onto the muffin cup and it's stuck to the pan, use a knife to gently loosen it.