Preheat oven to 350 degrees. Spray 12 muffin cups with cooking spray.
Line each cup with a ham slice, arranging to fit.
In a small bowl, beat an egg, and then pour it into a muffin cup. Sprinkle in some onion, some of the cheeses, and a sliced grape tomato. Continue until each muffin cup is filled. (You can mix all the eggs together with the veggies and cheese and divide the mixture into the cups for a faster method.)
Bake 20 to 25 minutes until eggs are set.
Remove from muffin tins (I used a butter knife to help loosen them) and sprinkle with parsley. Serve immediately.
Recipe by Simple, Sweet & Savory at https://www.simplesweetsavory.com/mini-ham-and-egg-frittatas/