Many cattle producers in this area seed tall fescue since it can grow in versatile soil conditions.  However, there are other options.  You will want to match the grass species to the natural resources of your land.  The  Pasture and Hayland Renovation Guide is a great resource.  There is also a free, online, self-paced course that includes a pasture renovation section, Introduction to Pasture and Grazing Management that you might find helpful.  Most grass seed for forages are grown locally in the Willamette Valley. They can be purchased at farm supply retail outlets and some farms that sell direct to customers.
Melissa