Preheat the oven to 350 degrees F. Generously spray 24 muffin cups (2 standard muffin tins) with cooking spray.
Crack the eggs into a bowl; add the salt, black pepper and chili powder. Whisk until combined. Add the ham, Cheddar, bell peppers and onions and stir.
With a measuring cup, scoop the mixture into the muffin cups. Bake for 20 to 22 minutes, until puffy and just barely set.
Within a minute or two, the casseroles will start to flatten just a little bit -- this is normal! Run a knife along the edges of each muffin cup and lift the casseroles out of the pan. Serve warm or at room temperature.
These casseroles freeze beautifully! Just flash-freeze them on a baking sheet, then transfer to plastic zipper bags. Thaw and reheat in the microwave when you're ready to serve.