There are lots and lots of ornamental grasses which have a history as food for grazers. Andropogon gerardii (Big Bluestem) and Schizachyrium scoparium (Little Bluestem) were once among the most plentiful prairie grasses.

Linked below is a terrific source of information about native prairie grasses.

Here is a link that might be useful: Prairie Frontier

Phleum pratense (Timothy Grass) is another possibility. The grass foliage stays quite short and isn't particularly interesting however the tall, strong seedheads, which form early and last a long time, are (IMO) quite decorative going thru stages of green, purple and brown/tan.

I knew this book would come in handy-someday. It's called Pasture and Range Plants put out by the Phillips Petroleum Company,1963. It says,
About Big Bluestem (A. gerardi):
"Few, if any, of the praire grasses can equal big bluestem in the quality or quantity of forage produced. It is relished by livestock and usually eaten in preference to other grasses in the mixture. Etc."

About Little Bluestem (S. scoparius [listed as A. scoparius]):
"This native grass provides nutritious grazing during the growing season and has been used for hay since the first days of settlement. Cattle have for many years been shipped from the south and southwest to fatten on the little bluestem ranges in the Kansas Fint[Flint?] Hills and the Osage hills of Oklahoma. Little bluestem produces from 3/4 to 2 tons of forage per acre and makes good winter grazing when supplemented with protein and minerals. Etc."

About Timothy(Phleum pretense):
"A native of Europe and Asia, timothy was commonly referred to in the New England states as "herd grass.""

"Throughout the area of its adaptation Timothy is grown extensively either alone or in mixtures with alfalfa and clover."

"This palatable, leafy grass is probably the most important tame hay grass in the United States and is more nutritious when cut in early bloom stage."

The book includes 59 species of grasses(native and introduced) if you want any more info.

Wow!

Thanks you all for the responses. You've been immensely helpful.

Just to add to the info, I found out from another friend that Miscanthus varieties are commonly used as forage plants in Japan.