For best texture, use rolled oats rather than quick oats so the mixture stays pleasantly chewy and not mushy, and mash the banana very well so its sweetness and “banana bread” flavor are evenly distributed. You can swap Greek yogurt for a dairy-free yogurt and use plant-based milk to make this vegan, or reduce the syrup or honey if your banana is very ripe and sweet. If the oats seem too thick in the morning, loosen them with a splash of milk; if too thin, stir in an extra spoonful of oats and let sit a few minutes. Add nuts and chocolate chips right before serving if you prefer them crunchier, and always store the oats in the fridge, enjoying them within 3 days for best flavor and quality.