In a 16-ounce mason jar or airtight container, combine the rolled oats, protein powder, chia seeds, and salt.
Whisk or stir the dry ingredients until the protein powder is evenly distributed to prevent clumping.
Add the Greek yogurt, almond milk, maple syrup, and vanilla extract to the container.
Stir vigorously or seal the lid and shake until all ingredients are fully incorporated and no dry pockets remain.
Seal the container and refrigerate for a minimum of 6 hours, ideally overnight.
Before serving, stir the oats to redistribute moisture and top with fresh fruit or nuts if desired.