Spray a 9" x 13" baking dish (or divide into individual serving pans) with vegetable spray. Place cubed bread, shredded cheese, chorizo, green peppers and mushrooms on bottom. In a mixing bowl, combine milk, egg, dry mustard and Northwood steak seasoning.
Scatter butter pieces on top of egg custard. Refrigerate for at least 5 hours. Place in a preheated 350°F oven and bake for 1 hour.