Combine 4 1/2 cups water, barley, oats, cornmeal, brown sugar, vanilla, cinnamon stick and 1/2 teaspoon salt in a slow cooker and cover and let sit overnight, at least 8 hours.
In the morning, set the slow cooker to high and cook until the grains are tender, about 2 hours, stirring once halfway through. Ladle the porridge into serving bowls and add your favorite toppings, such as milk, dried fruit, fresh fruit or nuts.
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