In a wide-mouth 16-ounce mason jar, combine the dry ingredients: rolled oats, protein powder, and chia seeds.
Add the Greek yogurt, almond milk, and vanilla extract to the jar.
Stir the mixture vigorously with a spoon until the protein powder is fully incorporated and no dry pockets remain.
Gently fold in the fresh blueberries to distribute them evenly.
Seal the jar with a tight-fitting lid and place in the refrigerator for a minimum of 6 hours, ideally overnight.
Remove from the refrigerator and stir once more before serving; if the consistency is too thick, add an additional splash of almond milk.