Preheat the oven to 400 degrees. Line 2 muffin pans with 18 cupcake liners.
In a bowl, stir together the milk, yogurt, and oats and allow to soak for 15 minutes.
In another bowl, whisk together the flour, baking powder, soda, salt, and cinnamon.
Whisk the coconut oil, eggs, maple syrup, brown sugar, and vanilla into the oat mixture until well combined. Add the dry ingredients to the wet ingredients and stir gently until just combined. Gently fold in the blueberries or other mix ins.
Scoop the batter into the prepared pans, filling each cup nearly to the top. Bake for 18-20 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool in the pans for 10 minutes before removing. These freeze great! Simply cool completely then place in a ziploc freezer bag. Reheat in the microwave before enjoying!