Best Route from Munchen to Interlaken, Switzerland

What countries is your pass valid in, or did you spend up and get the Global pass?

We have the global pass.

There are EC trains direct from Munich to Zurich at 7:17, 12:33, and 16:33 and take about 4 1/2 hours. From Zurich get a train to Bern then change to a train to Interlaken, that will take another 2 hours, 6 1/2 hours total. There is also a longer way (time wise) but more scenic route changing trains in Luzern.
There is also a way with only a single train change at Karlsruhe that takes 7 hours and 10 minutes, leaving Munich at 12:47.
Schedules at www.bahn.com

For fun you could go Munich - Innsbruck (or Salzburg), Innsbruck (or Salzburg via Innsbruck) - Zurich, Zurich - Luzern, Luzern - Interlaken.

Surely you will be going up the mountain so change at Interlaken Ost to Lauterbrunnen and then up either side of the valley, or stay in Lauterbrunnen. Having stayed 3 times in Interlaken before I started to stay up the hill I now repent and see the error of my ways.

That would get you plenty of scenic train rides on each leg, including the narrow gauge cog railway segment of the Golden Pass route (as they advertise it so heavily) but on a regular panoramic train (all included on your pass).

Or they arguably simpler Munich - Karlsruhe, Karlsruhe - Basel SBB, Basel SBB - Interlaken but less scenic, or the fastest choice (one hour faster than the Karlsruhe train route) is DB bus Munich to Zurich and the train onwards from there.....

The best way to find train schedules for almost all of Europe is the Bahn (German Rail) website http://reiseauskunft.bahn.de/bin/query.exe/en, following Rick's tutorial: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules

For Switzerland, the Swiss Rail website will not only have trains, but also buses, lifts, and other transit times. http://www.sbb.ch/en/home.html

Going from Interlaken to Munich, you can use either website to see all your options. You can then choose ones with fewer changes, shorter total times, etc.

Now for the part you didn't ask: don't stay in Interlaken, but instead, stay in the Berner Oberland villages (Lauterbrunnen, Wengen, Mürren, or Gimmelwald). Interlaken is near but not in the Alps, while the BO villages are in the Alps. The 20 extra minutes it takes to get from Interlaken Ost station to Lauterbrunnen are worth far more in terms of the quality of the experience you will have.

However, note that your Eurail Pass is not valid for full coverage past Interlaken Ost (there are large signs to this effect in the station, as you go to the platforms for Lauterbrunnen). You have to change trains here anyway, so just be sure to buy the correct ticket before boarding (you do get a reduction).

When I was booking a similar route (Murren to Munich, which will go right through interlakken) I found there isn't a great direct line. We chose o actually swing through Colmar/Strasbourg for 2 n to break up the trip.

Is the DB Bus from Munich to Zurich covered by the Global Eurail Pass?

We did this trip in reverse a while back. There is no quick easy way to do this trip.