Hi Steve,
Thank you for your question about fertilizing your lawn in Central Oregon.

The following OSU Extension publication provides information on overall lawn maintenance for our area and includes recommendations for fertilizing:
Lawn maintenance calendar for Central Oregon | OSU Extension Service (oregonstate.edu)

The OSU Deschutes County Extension website provides many helpful publications about gardening in Central Oregon, including a section on establishing and maintaining lawns:
Central Oregon Garden Publications | OSU Extension Service (oregonstate.edu)

If you need additional information, I recommend you call the Deschutes County OSU Extension office in Redmond at<personal data hidden> and ask to speak with Amy Jo Detweiler (oregonstate.edu). Amy Jo welcomes your home garden questions and is a great resource.