Place water, frozen berries, oats, honey, vanilla and cinnamon in a slow cooker and stir to combine. Cover and cook on high 4 hours or low 8 hours.
When cook time is complete stir in optional heavy cream and serve with toppings of choice.
Notes
This recipe is for steel cut oats and cannot be interchanged for old fashioned or quick cooking oats. If warming up leftovers stir in a little milk to help loosen the oatmeal up.