Add the old-fashioned oats, unsweetened almond milk, plain Greek yogurt, vanilla protein powder, chia seeds, and cinnamon to a mason jar or airtight container that is large enough to comfortably hold all of the ingredients while allowing room for stirring. Using a container with extra space makes it easier to combine everything thoroughly and helps prevent spills during mixing. Layering all the ingredients together at once simplifies preparation and makes this breakfast ideal for meal prep.

Using a spoon, stir the mixture thoroughly until all of the ingredients are fully incorporated and the protein powder is completely dissolved. Pay special attention to the bottom and sides of the container, scraping as needed to eliminate any dry pockets of oats, chia seeds, or protein powder. Continue mixing until the mixture appears smooth, creamy, and evenly combined. Taking an extra minute to stir properly ensures a better texture and prevents clumps from forming overnight.

Secure the lid tightly on the mason jar or airtight container and place it in the refrigerator for at least 6 hours, although overnight refrigeration is highly recommended for the best results. During this resting period, the oats will absorb the liquid, the chia seeds will expand and help thicken the mixture, and the flavors will blend together to create a creamy, satisfying breakfast with a pudding-like consistency.

When you are ready to enjoy your overnight oats, remove the container from the refrigerator and give the mixture a good stir. This helps redistribute the ingredients evenly, especially if some settling occurred during refrigeration. Stirring before serving ensures a consistent texture and flavor in every bite.

Check the consistency of the oats after stirring. If the mixture has thickened more than you prefer, gradually add a small splash of unsweetened almond milk and stir well until you achieve your desired texture. Some people enjoy thicker overnight oats, while others prefer a slightly looser, creamier consistency, so feel free to adjust according to your personal preference.

Top the overnight oats with fresh blueberries immediately before serving. Adding the berries just before eating helps preserve their natural sweetness, freshness, and texture while preventing them from becoming overly soft during refrigeration. Gently distribute the blueberries across the top so that each spoonful includes a burst of fruity flavor.

Enjoy the overnight oats cold directly from the mason jar for a convenient grab-and-go breakfast option. If you prefer a slightly less chilled breakfast, allow the oats to sit at room temperature for 5–10 minutes before eating. This can enhance the creamy texture and make the flavors more pronounced while still providing a refreshing and satisfying start to your day.