Interesting orchestra pieces to study

[Daevren]

Any suggestions. I have a few on my list already. I am going to buy FULL orchestra scores for study. So that I may learn and steal from the masters. The pieces should be rather modern. Sure, pre-Beethoven music is great, but I am really looking for things written in a more modern vocabulary.

Please don't just list your favorite pieces. I am looking for advice from people that have actually studied or looked into the topic of orchestration. The works could be concertos for piano, violin or anything else. But I think orchestra only pieces would generally have more value. 

[Nightscape]

I know its not an orchestra piece (so it can't teach you orchestration) but Bartok's Mikrokosmos is an invaluable tool is learning various modern compositional techniques.  You should be able to learn a lot about synthetic scales, polytonality, modality, and various other "tonal" modern techniques.  Of course, all of these can easily be applied to orchestral music.  Since it's in piano format - its easier to decipher and read than orchestral music too.

Generally, any orchestral work by Debussy, Ravel, Copland, and Stravinksy is also great for learning about orchestration and instrumentation.  These composers use instruments in traditional ways, and also experiment with newer instruments and intstrumental techniques.  But in particular, I would get Ravel's G major piano concerto (in full score), Debussy's Nocturnes for orchestra, Copland's Appalachian Spring, and also his 3rd Symphony (great for learning about flutes) and also Stravinksy's Petrouchka and perhaps Rite of Spring.  Also Stravinksy's later pieces are also good for learning about more conservative/simplified orchestration procedures.

But don't overlook Chamber Music either.  If you want to know about the stringed instruments, Bartok's String Quartets (esp 3-6) are among the best to study.