I live in CA but commuted to a branch office in Oregon some days in the year. Do I need to file a non-resident status in Oregon though the W2 shows only CA?

It depends.  California and Oregon do not share a reciprocity agreement (FAQ below has more information), so you may need to file an Oregon return: https://ttlc.intuit.com/replies/4776822

The following link has information on what Oregon considers Oregon Income (Click on link, and in the “Filter by Search” Box type “Oregon Income” Find the question: Are wages paid to nonresident employees subject to withholding?)

To see if part of your income is considered earned in Oregon, you may wish to contact your payroll department.  If it is, you will likely want to have taxes withheld for Oregon.  You also would want to ask them to issue you a corrected W-2 showing what income in Oregon income.

Even if the income you earned at the Oregon office is Oregon income, you still may not have to file an Oregon return if you are below the Filing Requirements. (Click on link for Oregon non-resident filing threshold).

Regardless of whether or not some of your income is taxable to Oregon, it will all be taxable to California.  But don’t worry; California will issue a credit for taxes you must pay to Oregon on the same income (so you’re not taxed twice)

More good news:  you likely can claim employee business expenses for your travel and stay (if necessary) in Oregon, as long as these expenses were not reimbursed by your employer.  Note the FAQ below for more information:  https://ttlc.intuit.com/replies/3300622