01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, whisk together whole wheat flour, rolled oats, protein powder, sugar, baking powder, baking soda, and salt.
03 - Whisk eggs, applesauce, Greek yogurt, milk, and vanilla extract in a separate bowl until smooth.
04 - Pour the wet ingredients into the dry ingredients and mix gently until just incorporated. Avoid overmixing.
05 - Gently fold mixed berries into the batter.
06 - Scoop 1/4 cup mounds of batter onto the prepared baking sheet, leaving at least 2 inches between each.
07 - Bake for 13 to 15 minutes until muffin tops are lightly golden and a toothpick inserted into the center comes out clean.
08 - Allow muffin tops to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.