goes to show how non-standard the volume measurements are. The nutrition facts label on oatmeal says 1/2C=40g. When I don't have my scale, and have to use a measuring cup, I definately can't fill it full for 40g.
Edit: I wonder if the 156g for 1c = cooked and not raw
here's what nutritiondata.com says:
Nutrition Facts and Analysis for Cereals, oats, regular and quick and instant, not fortified, dry [oatmeal, old-fashioned oats, rolled oats] - dry