Ham and Cheese Strata

3 cups day old Italian bread, cubed
8 oz. sharp cheddar cheese, shredded
3 cups cooked ham, cubed
8 eggs, lightly beaten
3 cups milk
1 tbsp. dry mustard
3 tbsp. flour
1/2 cup finely chopped onion

Beat eggs. Add milk, flour and mustard. Beat until smooth. Add cheese, ham, onion and bread. Pour into a 9x13 inch pan, cover and refrigerate overnight. Bake at 325 degrees 45 minutes to 1 hour.