In a medium bowl or mason jar, add rolled oats, protein powder, chia seeds, and cinnamon. Mix well to evenly distribute the protein powder and prevent clumps.
Pour in almond milk, maple syrup, and vanilla extract. Stir thoroughly until the mixture looks smooth and well combined.
If the mixture feels too thick, add 1–2 tablespoons of extra milk. The oats will continue to thicken as they chill.
Cover the jar or bowl with a lid and place it in the refrigerator for at least 6 hours or overnight. This allows the oats and chia seeds to absorb liquid and soften fully.
In the morning, give the oats a good stir. Add your favorite toppings and enjoy chilled, or warm gently if preferred.