Spray a 9×13” casserole pan with non-stick spray or line with parchment paper.
Cut whole grain bread slices into 1-inch cubes. Place bread cubes into the casserole pan.
In a large bowl, whisk together eggs, milk, vanilla, pumpkin pie spice, and pumpkin puree until well combined. Pour mixture over bread until all bread is covered. Cover and refrigerate for 15 minutes or overnight.
When ready to bake, preheat oven to 350 degrees F. Mix together brown sugar and pecan halves. Uncover casserole. Using clean hands, top with sugar and pecan mixture. Bake for 35 to 45 minutes or until golden brown and no longer wet.
Serve with maple syrup.
Store leftovers in the refrigerator for a couple of days.