Add all of the shredded mozzarella and 1/2 cup of the shredded cheddar cheeses to a medium (quart) freezer bag. Remove excess air, seal and freeze.
Add remaining ingredients to a large freezer bag. Squish gently to mix.
Remove excess air, seal and staple the two bags together above the seal. Freeze.
Thaw overnight in the fridge.
Empty large bag into a casserole dish. Top with cheese from the smaller bag. Bake at 350° for 20-30 minutes.