In the Personal Info section of TT, indicate that you had "Other State Income" from MT. This will prompt the program to generate a non-resident MT tax return. MT can tax the income you earned in MT; your home state of OR can tax ALL your income, including that from MT. As @Hal_Al stated OR will grant you an "other state credit" for the taxes you pay to MT, so in effect you won't be double-taxed.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
