Preheat your oven to 350°F / 175°C. Lightly coat a 3-quart casserole dish or baking pan with cooking spray.
In a large bowl, whisk together the milk, egg and egg whites, applesauce, maple syrup, vanilla, baking powder, cinnamon, nutmeg, and sea salt until well combined.
Stir in the rolled oats, oat bran, and chopped pecans.
Gently fold in half of the blueberries (about ¾ cup / 180 ml / 6.1 fl oz).
Scatter the remaining blueberries across the bottom of your prepared casserole dish.
Pour the oatmeal mixture into the dish over the blueberries and spread evenly.
Bake, uncovered, for 35 to 40 minutes, or until the edges are golden brown and the center is set.
Let cool slightly before slicing and serving.