Any advice? I'm at 3000' elevation, approx. 11" annual rainfall with most all of it coming in winter/spring, annual low @ 15F and 1000 chilling hours. This pasture will be irrigated and planted in the understory of a young orchard and be grazed on a paddock-shift of rabbits and chickens.
Here's some info on crested wheatgrass, which can be beneficial, but since it is an introduced species it can be detrimental to native grasses.
Here's another reference with a lots of photos of different grass species.
Another resource is the Bureau of Land Management. They are in the business of keeping public grasslands in good shape, so why not benefit from their expertise. Here is a presentation that covers their recent practices.
If you are going to be combining pasture with orchard, it would make good sense to include legumes in with the grasses, because of their ability to provide the trees with nitrogen. Winter peas would be a good choice to seed in the fall, as that will make good use of your rainfall pattern.