Grease a baking dish and spread the bread cubes evenly across the bottom. Sprinkle the cooked bacon and cheddar cheese over the bread.
Whisk together the eggs, milk, Dijon mustard, garlic powder, salt, and pepper until smooth.
Pour the egg mixture evenly over the bread. Press the bread down gently so it absorbs the liquid.
Cover the dish and refrigerate overnight or for at least 8 hours.
Bake at 350°F (175°C) for 40 to 45 minutes until the center is set and the top is golden brown.
Let the casserole rest for 10 minutes before serving. Cool completely before freezing leftover portions.