Place bread into a large bowl.
Pour milk over bread and mix well, breaking bread up while mixing. Mixture should look like wet oatmeal.
Set aside while preparing the rest of the ingredients.
Mix together the eggs, sugar, vanilla and cinnamon.
Add egg mixture to milk soaked bread. Mix well and set aside.
Let mixture set for at least 2 hours. Stir mixture every 15 minutes or so.
Spray 9X13 pan with baking spray.
Place butter into pan.
Preheat oven to 350 Degrees F. Place pan with butter into oven while preheating.
Remove pan when butter is completely melted.
Pour pudding mix into heated pan and place into preheated oven.
Bake for 45 to 60 minutes, or until pudding is set and browned to your preferred color.
Remove from oven and allow to cool slightly before cutting.