Grease a 9x13 baking dish and add bread cubes evenly.
In a bowl, whisk the eggs, milk, sugar, vanilla, cinnamon and nutmeg together.
Pour the mixture over the bread cubes. Make sure everything is coated!
Cover and refrigerate overnight (or at least a few hours)
When ready to bake: preheat to 350F
Mix the streusel topping by combining butter, brown sugar, flour and cinnamon until a crumble forms.
Sprinkle on top and bake for 45-55 minutes (depending on how crispy you like it)
If the top of the French toast bake is getting dark, you can cover it with foil to prevent too much browning.