Butter a 9x13-inch baking dish. Lay the bread slices into the prepared baking dish in 2 layers. Beat eggs, half-and-half cream, orange juice, white sugar, brown sugar, cinnamon, and nutmeg together in a bowl until smooth, and pour over the bread. With a large spoon, press the bread down into the egg mixture so all the bread becomes soaked with the mixture.
Sprinkle the granola evenly over the casserole, and drizzle with maple syrup and melted butter. Cover the dish with plastic wrap, and refrigerate overnight.
About 1 hour before serving, remove the casserole from the refrigerator, and take off the plastic wrap. Preheat oven to 300 degrees F (150 degrees C).
Bake in the preheated oven for 30 minutes, then turn oven temperature up to 375 degrees F (190 degrees C). Bake the casserole until browned, about 15 more minutes. Serve warm.