Preheat the oven to 350°F. Grease a muffin pan with nonstick cooking spray and set aside.
In a small bowl, combine the ground flaxseed and water. Let sit while you prepare the other ingredients.
In a large bowl, combine the oats, baking powder, salt, and cinnamon. Set aside.
In a medium bowl, combine the mashed banana, flaxseed mixture, melted coconut oil, almond milk, maple syrup, and vanilla extract.
Add the wet ingredients to the dry ingredients and mix to combine. Gently stir in the blueberries. Pour the mixture into the prepared muffin pan, filling each cup evenly. Bake for 23-25 minutes or until the cups are a golden brown. Remove from the oven and let the muffins cool in the pan for 5 minutes. Remove from the pan and serve warm.
Note-if you don't need the recipe to be vegan you can use one egg instead of the flaxseed and water mixture. The oatmeal cups will keep in the refrigerator for 2-3 days in an airtight container or in the freezer for up to 1 month. Reheat in the microwave.