Preheat oven to 350F. Line or grease muffin tins with cooking spray.
Mash bananas in a large mixing bowl with a fork.
Combine bananas, nut butter, Greek yogurt, eggs, vanilla extract, and maple syrup. Stir to combine.
To blend oats, add old fashioned oats to blender. Blend until it has a flour consistency, approximately 30 seconds.
In a separate bowl, combine blended oats, collagen peptides, baking soda, baking powder, and sea salt. Stir to combine.
Add dry ingredients to wet ingredients. Stir to combine. Gently mix in blueberries.
Pour batter into prepared muffin tins. Top with additional blueberries, if preferred.
Bake for 22-25 minutes, or until a toothpick inserted in the center comes out clean.
Cool for 10-15 minutes. Store in the fridge in an airtight container for up to a week or in the freezer for up to 6 months.
Serve cold or warm and top with additional nut butter, if desired.