Fill a ceramic bowl with raw oats groats, cover with water, and allow to soak overnight.
Next, blend the oat groats and soaking water really well in a blender until smooth and creamy (NOT WATERY). Your oats should resemble thick cooked oatmeal:
Pour the raw oatmeal back into your ceramic bowl, cover with a paper towel or other breathable material, & place in a warm area. I like to use my Costco HeatDish set on low.
Now, simply allow your oats to ferment. Stir occasionally, and if they become to dry, add a little water. I usually allow mine to ferment for 48 hours – just depends on how tangy you want them to taste.
Your oatgurt will not go bad, but it will get more sour everyday as the beneficial flora continues to grow. When they have reached optimal sourness, either eat your oatgurt or place in the fridge to stop the fermentation process.