Step 4: Ferment
As this stuff soaks, Lactobacilli and other lactic acid bacteria will consume sugars and starches producing lactic acid, lowering the pH of the mixture. This acid environment is inhospitable to the bacteria that cause spoilage and food poisoning.
You'll want to let it soak for at least 24 hours, or let it go for as long as a week (maybe longer, but I'm not sure what will happen to it). The longer you let it ferment, the more acidic it becomes and the more sour it tastes. It will begin to smell sour, too. Bubbles may form, because Lactobacilli also create CO2 as a waste product.
You may want to stir up the mixture every day or so, mainly so the stuff on the top doesn't get dry.
At any point along the way, you can just eat this stuff as oatmeal. In fact this is the same way I make oatmeal, I just don't dehydrate it.
-Grains, nuts, and seeds contain phytic acid, a form of phosphate that is not bioavailable to humans (we can't absorb it). Additionally, phytic acid binds up minerals like magnesium, calcium, iron, and zinc, and the vitamin niacin. Because of this it is considered an "anti-nutrient." Lactobacilli contain the enzyme phytase which breaks down phytic acid, freeing up nutrients so we can absorb them. According to Wikipedia, lactofermentation is more effective than cooking at removing phytic acid.
-Nuts contain enzyme inhibitors which prevent them from sprouting in adverse conditions (dryness). If eaten in great quantity, this can supposedly strain your digestive system. Soaking the nuts neutralizes the enzyme inhibitor (the nut thinks it's getting rained on).
-Starches are broken down into simple sugars and into lactic acid which are more digestible. It's the same thing that happens in your digestive tract, but this way we get it started in a jar first.
-There's a ton more info out there about why lactofermented food is good for you, but no need to list it all here.
-Lactic acid preserves food. I would expect our end product to stay good for a really long time, but of course I don't know because I always eat them pretty fast (I guess baked granola lasts plenty long as well).
-I like the taste better, you might not.