Comment by Marsymars
It's quite a bit of volume, but it's "only" about 1000 Calories if it doesn't have any oils/sugar added.
I'd guess the easiest way to get it down would be to just blend the oats into water without cooking so you have something that you can just drink like water.
Wasn't that basically what Soylent was? With a ground up multivitamin and some oil drizzled in?