Butter bottom and sides of a 13x9 baking dish.
Trim crust from bread.
In medium size bowl, mix together the sharp cheddar cheese spread and butter or oleo. Spread this mixture on both sides of the bread and place in the greased 13x9 baking dish. Push the slices together – they will fit.
Beat together eggs, milk, mushrooms, onions, salt, pepper, and diced ham. Pour egg mixture over bread slices coated with cheese spread mixture.
Cover baking dish tightly and let set in refrigerator 8 hours or overnight.
Remove from refrigerator ½ hour before baking. Then place uncovered in COLD OVEN. Bake until center is set, about 1 hour at 350 degrees F (175 degrees C). Allow to sit and cool 15 minutes before serving.