True, but that much oatmeal will likely stay with you for a long time. I basically have figured out that appetite stimulating foods are those high in carbs and moderately low to very to in protein and fats with a moderate to low amount of fiber. There's only two different times in the day that those kind of calories can be consumed without worry of fat deposits - first meal and PWO.
With all that considered, I've noticed two really good bulking meals that serve as a high calorie adder w/ appetite stimulating effects when eaten in the morning and PWO.
Cream of wheat/rice
Local Honey
Banana or other fruits
Depending on how much wheat/rice you use, and given (1) banana and (2) TBSP of honey your looking at anywhere from 450-750 calories.
Thomas Hearty Whole Grain Bagels - 250 calories
JIF Omega-3 Peanut Butter - 190 calories per serving
Local Honey - 60-120 calories
500-560 kcals, only this one is relatively low in fat at somewhere around ~ 10g fat total (between 16-19% fat calories). The rest is mainly carbs and about 12-15% of the meal is made up of protein.
Needless to say these meals slide right through you. Especially the Cream of Rice setup since it actually has zero fat it in. Stuff doesn't stay in the stomach long! These meals eaten first thing in the AM is almost like it never happened, appetite-wise.