Voles, particularly the gray-tailed species, are one of the most abundant wildlife residents on the Willamette Valley floor - particularly in the former grassland and oak savannah areas. I say that because total eradication from a rich area (such as your yard) within their native range is unlikely. However, they are relatively easily trapped with mouse-sized snap traps set such that the treadles (trigger, and look for the model with the broad yellow "cheese") lie across the travel path at burrow entrances - Setting that way allows an animal to encounter the trap going into or coming out of the burrow. If your landscaping allows, deep tillage can disrupt existing burrow systems - and will likely kill a few of the current animals. 
Raised beds can be protected by lining the bottom with unchewable hardware cloth (1/2" grid). Above-ground stems of individual plants such as shrubs can be protected by collaring them above and below-ground with the same material. Some people will protect new plantings with hardware cloth "baskets" to protect roots, but the basket needs to be large enough to allow for full (mature-extent) root growth in order to allow the plant to do well.
Few commercially-available products have been subjected to replicated trials of effectiveness, but Plantskydd's makers have some efficacy (against voles) data, so that is one option to consider - however even then, realize that spray-on product doesn't "soak" in to protect roots.