In a 16-ounce mason jar or airtight container, whisk together the rolled oats, protein powder, and chia seeds until evenly distributed.
Add the Greek yogurt, almond milk, vanilla extract, and maple syrup to the dry ingredients.
Stir vigorously until the protein powder is fully dissolved and no dry clumps remain.
Gently fold in half of the fresh raspberries, slightly crushing a few to incorporate their flavor into the mixture.
Seal the container with a lid and refrigerate for a minimum of 6 hours, or ideally overnight.
Before serving, stir the mixture once more to redistribute moisture and top with the remaining fresh raspberries.