Creating the Ham and Cheese Breakfast Casserole is straightforward when you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or butter.
2. Whisk Eggs: In a large mixing bowl, whisk together the eggs, milk, salt, pepper, garlic powder, and onion powder until well combined.
3. Combine Bread and Ham: In a separate bowl, mix the cubed bread and diced ham until evenly distributed.
4. Add Cheese: Gently fold in 1.5 cups of shredded cheese into the bread and ham mixture.
5. Layer in Dish: Spread the bread, ham, and cheese mixture evenly in the greased baking dish.
6. Pour Egg Mixture: Pour the egg mixture over the bread and ham, ensuring it is evenly soaked.
7. Sprinkle Remaining Cheese: Top with the remaining 0.5 cups of shredded cheese and chopped green onions, if using.
8. Bake: Place in the preheated oven and bake for 30-35 minutes or until the eggs are set and the top is golden brown.
9. Cool: Remove from the oven and allow to cool for 5-10 minutes before slicing and serving.

These simple steps will guide you in creating a delicious Ham and Cheese Breakfast Casserole effortlessly.