Grain has to be processed to be efficient as a source of nutrition. Once you have ground meal or flour, you can either use it in a stew or porridge, or you can make bread / flatbread out of it.

Grain that's been processed into flour or meal packs more nutrition into the same volume than an equivalent volume of unprocessed grain. So then the question is, how do you want to prepare it?

Bread is storable (depending on the stability of the other ingredients). And unlike something like porridge (also a processed grain-based food) many types of bread are portable.

So you have a nutritionally dense, portable food resource that can be produced and stored in advance of need, and it can be made simply by adding water to flour and placing it near a fire.