Preheat the oven to 350°F (175°C).
In a large mixing bowl, whisk together the eggs and milk.
Add salt, pepper, garlic powder, and onion powder to the egg mixture.
Stir in the shredded cheese, cooked bacon, bell peppers, and spinach.
Grease a 9x13-inch baking dish with cooking spray.
Pour the egg mixture into the prepared baking dish.
Spread the mixture evenly across the dish.
Bake in the preheated oven for 35-40 minutes, or until the center is set.
Remove from the oven and let it cool for 5 minutes.
Slice into squares and serve warm.