In a large bowl, combine all the ingredients, stirring until fully incorporated.
Transfer the mixture to an airtight container and refrigerate for at least 3 hours, or preferably overnight. The longer the oats sit, the softer and more flavorful they become.
When ready to serve, give the oats a quick stir. Top with a dollop of Greek yogurt, a drizzle of maple syrup, and a sprinkle of additional nuts or granola.