I don't know what Mongolian beef is, but I do know one thing. It's not Mongolian. I spend about 2 months a year in Ulaanbaatar, have done for the past 4 years and I have never seen Mongolian beef as served in US restaurants. As the poster above says, they usually eat lamb (mutton) which from my experience is best avoided.

I'm in Ulaanbaatar at the moment, and since my last visit (September 06) a very funny thing has happened. Someone has opened a Mongolian Barbecue restaurant. This has caused much discussion among the local population, as they can't understand what's Mongolian about it.

Doug