Preheat your oven to 350°F (175°C) and lightly grease a standard 12-cup muffin tin with a little coconut oil or line with parchment liners.
In a large mixing bowl, peel the bananas and mash them thoroughly with a fork until they reach a smooth, liquid-like consistency.
Whisk the unsweetened almond milk and vanilla extract into the mashed bananas until well combined.
Add the rolled oats, vanilla pea protein powder, chia seeds, ground cinnamon, baking powder, and sea salt to the wet ingredients.
Stir the mixture with a large spoon until all the dry ingredients are fully incorporated and the batter is thick.
Gently fold in the fresh blueberries, being careful not to crush them so they remain whole for baking.
Distribute the batter evenly among the 12 muffin cups, filling each nearly to the top.
Bake for 20 to 25 minutes, or until the tops are golden brown and feel firm to the touch.
Allow the oatmeal cups to cool in the tin for 10 minutes before transferring them to a wire rack to cool completely.
Store in an airtight container in the refrigerator for up to 5 days; serve 4 cups per breakfast to hit your daily meal prep targets.