We have a Bernese-Orberland pass---and want to go to Italy. How do we get from Murren to Orta?
I don't know how far the BO pass will get you on your way out of Switzerland. That being said, I'm linking you to a Trenitalia train schedule from Interlaken Ost to Orta-Miasino (Trenitalia will not show Muerren). You can see the times. Just add another 40 minutes or so to get from Muerren to Interlaken Ost.
CLICK HERE to see the schedule.
Your Swiss rail pass should get you to Domodossola. If you check the DB site you will find that there is also a bus connection from Domodossola.
Please mind that the Swiss Pass is different than the berner Oberland pass.
Jeff and aRies are both correct. For your question, your BO pass will not get you beyond the Berner Oberland. A Swiss pass that is good throughout the country will be good to Domodossola. The two are different types of passes.