How many Calories are in a cup of rolled oats???

Ok, here's why I ask...

I did a test and got;

quaker, walmart, price chopper all say "300"

generic Cereals - Oats, regular and quick and instant, not fortified, dry (oatmeal, rolled oats), 1 cup says "311"

whole foods organic says "330"

Sprouts Market (my brand) says "380"

Trader Joe's - Rolled Oats, 1 cup dry jumps all the way up to a whopping "450"!!!!

Can there really be this variance in plain rolled oats?

and for my own personal selfish concerns..., is the sprouts brand really going to have 80 more calories that quaker?? If so I would probably switch brands and buy from costco instead, the thing is.... I doubt it.