When hot liquids are added to the oats, there is a swelling of the starch granules that are rehydrated and gelatinized. Its like a muscle...add water to the body (as well as other liquids) and it will HYDRATE the muscles. Thus, it is the same muscle, but rather more "hydrated".
The primary goals of cooking oats are to improve digestibility, gelatinization of the starch granules, and to improve flavor (which will vary between individuals as Enock has mentioned as he/she likes the oats uncooked).
Water will help rehydrate the starch granules, and during cooking, the starch granules absorb the water and swell enormously...gelatinization. The heating of this mixture also creates steam within the kernel of the oat and helps break apart the oat which will help increase digestibility. The soluble fiber will then be exuded from the granules and help with the thickening of the mixture.
If eaten without cooking, you may want to run the oats through a coffee grinder or something to physically break down the oat kernels. This may help with the digestibility of the soluble fibers and other nutrients trapped within the kernel.
The reason why cooking the oats usually results in a more "pleasant" taste is because of the starch being converted into both dextrins and SUGAR. These outcomes along with the gelatinization helps with the flavor. I guess if you wanted, you could just add some sugar or artificial sweeteners to the uncooked portions, thus giving a sweeter flavor.
Well, gotta go eat some christmas dinner...later, and i'll come back here later. BYE!
MR. BMJ