Yes, if you are a resident of Oregon you have to report the MI K-1 on your OR tax return. 

States that have an income tax will tax their residents on all income, no matter where earned. When out-of-state income is taxed by  non-resident state, your home state will give you a credit - against your home state tax - for any tax paid to the non-resident state on the same income. That approach prevents "double-taxation" (for the most part.

FAQ - When would I have to file returns in more than one state?