Heat oven to 350 degrees. Coat a 9x13 inch baking pan with cooking spray and set aside.
Add potatoes, ham, and cheese to a large bowl. Toss to combine and add the mixture to the bottom of the prepared baking dish.
In a large bowl, whisk together eggs, milk, salt, onion powder, garlic powder, and pepper. Pour mixture over potatoes, ham, and cheese. Using the back of a spoon, press everything down, so the egg mixture covers all the ingredients.
Bake for approximately 1 hour, checking at the 50-minute mark. The center should be set and the edges golden brown.
Remove casserole and allow to cool for 10 minutes. Sprinkle on chopped chives, slice, and serve.