Now that I have shared the basic recipe with you, there are alternatives to the ingredients above based on what you have on hand. You can seriously just be creative! Basically, anything you would put into an omelet would be perfect! We make omelets or this casserole towards the end of our grocery week to use up any final veggies we have left to minimize food waste (same with end of the week stir-frys and soups!).
So open your fridge and look to see what you have, but here are some additional ideas:
Bacon
Sausage links or crumbles
Lunch meats
Left over chicken, beef or steak
Bell peppers
Celery
Greens like spinach, kale, basil, arugula, cilantro, parsley, etc.
Cheese of any kind - but we also love feta/goat cheese!
Cabbage
Onions of any kind
Potatoes or hash browns
Any old breads like french, bagels, or even leftover heels
Please note, if you are using veggies, we would recommend a light saute' on them before adding to the casserole.