I haven’t been able to find a good guide on identifying edible wild grains, although I have done a little experimentation. A lot of wild grasses you find around are imports from europe that were brought over for livestock forage, so most of them are edible. Pretty much any Bromus species are worth collecting because of their large grains. Many species of Bromus in California are semi-domesticated due to native american land management over the last 10 thousand-plus years. I have heard accounts that some species contain cyanide compounds, but I have not a clue as to which.
I collected some unknown grass species recently and fried up the seeds to remove the chaff. The seeds were delicious and could have been pounded into a flour, but I chose to just eat them by the handful. A good book that outlines wild grain processing is “Tending the Wild” by M. Kat Anderson. I’d recommend this book to anyone and everyone.
Also indian ricegrass. Quite productive, but doesnt grow very tall. And ai have heard that there are multiple other wild rices and ryes. Ai personally grow several species of wild rye. Another one, with wide range, is the invasive arundo (giant reed).
All species. Cooking or fermenting gets rid of most, but not all. Thats why the “paleo” diet excludes grass seeds. But most (if not all) tribes accross the world have eaten grass seeds of most kinds, especially as famine food (but always cooked or fermented). In general, if its easy to harvest, big or you just really need it, its edible.
Happy harvests Kveldulf!