In a jar or glass container combine oats, protein powder, a pinch of salt, and milk. Add sweetener and vanilla extract if using unflavored protein. Optionally, you can also add chia seeds.
Stir everything well using a spoon or fork. Make sure to mix from the bottom up, oats can settle and stick at the bottom.
Cover the container with a lid or seal tightly with plastic wrap or aluminum foil.
Refrigerate the oats for at least 2 hours, or overnight for the creamiest result. Store them on a shelf rather than the fridge door to avoid frequent changes of temperature.
Before serving, give the oats a good stir from bottom to top. Add your favorite toppings and dig in!