You can always use pre-measured powder - either protein powder or an LC-friendly meal replacement powder - esp. if you have some way to get your water really cold. I've found a strawberry-banana MRP that comes in at 21gPRO/10gCHO/2.5gFAT and is really tasty.

Otherwise jerky+nuts comes to mind as trail snacks. If you are burning alot of cals, I think you can also afford more carbs per day - so if you can't stand the LC cereals - go for chex or other regulars.

If long-cook oatmeal is too much time for breakfast (esp at altitude) - try oat bran - cooks in about 2 mins for 1 serving at sea level - and stir in lots of cinnamon and a good tasting vanilla or plain protein powder for a protein boost.

Also - if you are out for just a day (not extended packing) - hardboiled eggs or whites should hold up OK, esp. if it is cold out.