My power food for big ride days:

7-grain (or more) cut cereal (not rolled like traditional oatmeal) with added sliced almonds and raisins. Might eat a hard-boiled egg if ride start time isn't until late in the morning.

I must have carbs or my glycogen stores poop out. I need a small amount of protein and lots of high fiber carbs. Your stomach takes longer to digest fiber so unprocessed cut-grain cereals are far more nutritional with even a bit more protein than regular oatmeal. Plus, you can have a lot of good stuff like flax seed in there. Add some nuts and fruit, and you've got a good ride day meal that is easily digestible and sticks to your ribs.