Pick your jar or container. A 12–16 oz jar or lidded bowl works well and gives room for stirring and toppings.

Mix the dry base. Add rolled oats, protein powder, chia or flax, and a pinch of salt to the container. Stir to distribute the powder so it doesn’t clump later.

Add liquids and flavor. Pour in milk, then add Greek yogurt (if using), vanilla extract, and your sweetener. Stir until the mixture looks smooth and the protein powder is fully dissolved.

Fold in the berries. Use fresh or frozen mixed berries. If using frozen, there’s no need to thaw; they’ll soften overnight and release juices that color and flavor the oats.

Adjust consistency. The mixture should look a bit loose—like a thin batter. If it’s very thick, add a splash more milk. The oats and chia will absorb liquid as they sit.

Cover and chill. Seal the container and refrigerate for at least 4 hours, but ideally overnight (8–12 hours) for the creamiest texture.

Stir and top in the morning. Give it a quick stir. If it’s thicker than you like, add a little milk. Finish with your favorite toppings: a spoon of almond butter, crunchy nuts or seeds, extra berries, or a sprinkle of lemon zest for brightness.

Serve cold or warm. Overnight oats are meant to be eaten cold, but you can warm them gently in the microwave for 30–60 seconds if that’s your preference. Add a splash of milk after heating to keep them creamy.