Preheat oven to 350 degrees F (175 degrees C) and grease a standard 12-cup muffin tin with cooking spray or oil.
In a large mixing bowl, whisk together the rolled oats, baking powder, ground cinnamon, and salt until evenly distributed.
In a separate medium bowl, whisk together the eggs, maple syrup, milk, melted coconut oil, and vanilla extract until well combined.
Pour the liquid mixture over the dry oat mixture and stir with a spatula until the oats are thoroughly coated.
Gently fold 1 1/4 cups of the blueberries into the batter, taking care not to crush them.
Distribute the batter evenly among the 12 muffin cups, filling each nearly to the brim.
Press the remaining 1/4 cup of blueberries into the tops of the batter-filled cups for presentation.
Bake for 25 to 28 minutes, or until the centers are set and the edges are lightly golden brown.
Remove from the oven and allow the cups to cool in the pan for at least 10 minutes to ensure they maintain their structure before removal.