Add oats, milk, yogurt, protein powder, chia seeds, lemon zest, maple syrup into a bowl or jar and stir together. Gently stir in the raspberries.
Cover and place in the fridge overnight. If you’re in a rush you can shorten the soak time to 2-4 hours.
The next morning (or when ready to eat), remove the lid and give the oats a big stir. If they seem too thick you can add a little more milk to loosen the mixture. Top with additional raspberries and serve.