Preheat the oven to 350°F. Grease a 9x13-inch baking dish with olive oil or cooking spray.
In a large bowl, whisk together the eggs, milk, garlic powder, onion powder, salt, and black pepper.
Add the cubed bread, diced vegetables, and half of the cheese to the egg mixture. Stir until well combined.
Pour the mixture into the prepared baking dish and spread it evenly.
Sprinkle the remaining cheese on top.
Cover the dish with plastic wrap and refrigerate for at least 2 hours or overnight.
When ready to bake, remove the plastic wrap and bake for 30-35 minutes, or until the casserole is set and the top is golden brown.
Let it cool for a few minutes before slicing and serving.