In a skillet, brown and crumble sausage; drain and set aside.
In a large bowl, beat eggs; add milk, salt and mustard.
Stir in bread cubes, cheese and sausage.
Pour into a greased 11-in.x 7-in.x 2-in.baking dish.
Cover and refrigerate for 8 hours or overnight.
Remove from the refrigerator 30 minutes before baking.
Bake, uncovered, at 350° for 40 minutes or until a knife inserted near the center comes out clean.