In order to conevert starches, they must be soluble in water (gelatanized). Luckily, barley and wheat gelatinizes at mash temperatures. Grains like oats, corn and rice gelatinize at higher temps. When using regular forms of these adjuncts, something called a cereal mash is required. All that really means is that the grains need to be cooked, or boiled.
Luckily for us, flaked versions of these adjuncts exist. You can add flaked grains directly to the mash. During the "flaking" process, grains are sent through heated rollers. The rollers instantly gelatinize the starches. Most recipes call for flaked oats. You can also find them as quick, or instant oats in the grocery store.
Here is what Palmer says: Other Grain adjuncts