Brown breakfast sausage in skillet, breaking into crumbles. Drain on paper towels.
Grease 9x13 dish. Spread half the bread cubes, half the sausage, half the cheese. Repeat with remaining bread, sausage, cheese.
Whisk eggs with milk, salt, pepper, and dry mustard. Pour over layers and press down lightly.
Cover and refrigerate at least 8 hours, ideally overnight.
Rest at room temp 30 minutes. Bake uncovered at 350 degrees for 45 to 50 minutes until center is set and top golden. Rest 10 minutes before serving.