Prepare your slow cooker by lightly coating the inside with cooking spray or butter. This prevents sticking and makes cleanup easier.
Peel and cube the butternut squash into approximately 1/2-inch pieces. Smaller pieces will cook more thoroughly and blend better with the oatmeal.
Add all ingredients to the slow cooker – oats, cubed butternut squash, liquid of choice, maple syrup, vanilla, cinnamon, nutmeg, and salt. Stir well to combine.
Cover and set your slow cooker to low for 7-8 hours. The long, slow cooking process allows the squash to break down and the oats to become perfectly tender.
Give everything a good stir when you wake up. The squash should be very soft and will partially dissolve into the oatmeal, creating a creamy consistency.
Serve warm with your favorite toppings. A drizzle of additional maple syrup, a splash of milk, and some chopped nuts add wonderful texture and flavor.