In a 16-ounce mason jar or airtight container, combine the rolled oats, protein powder, and chia seeds.
Stir the dry ingredients thoroughly to ensure the protein powder is evenly distributed.
Add the almond milk, Greek yogurt, and vanilla extract to the jar.
Stir the mixture vigorously until no dry clumps of protein powder remain and the yogurt is fully integrated.
Seal the container with a lid and place it in the refrigerator.
Refrigerate for a minimum of 6 hours, though 8 to 12 hours is recommended for optimal hydration.
Remove from the refrigerator, stir once more to redistribute moisture, and serve chilled.