In a mixing bowl, combine rolled oats, milk, Greek yogurt, honey or maple syrup, vanilla extract, lemon zest, and lemon juice. Stir until well combined.

Divide the mixture evenly into jars or containers with lids. Seal and refrigerate overnight (or at least 4 hours) to allow the oats to soak up the liquid.

In the morning, give the oats a good stir. Add your choice of toppings such as fresh berries and nuts or seeds before serving.