In addition to the oil content, granola is cooked. So it would be like making a beer with 100% specialty malts.
Right, but there's no reason not to make a granola-themed brown ale with 30-50% specialty grains.
Here is alton brown's recipe:
3 cups rolled oats
1 cup slivered almonds
1 cup cashews
3/4 cup shredded sweet coconut
1/4 cup plus 2 tablespoons dark brown sugar
1/4 cup plus 2 tablespoons maple syrup
1/4 cup vegetable oil
3/4 teaspoon salt
1 cup raisins
Leave out the oil and salt
Replace the rolled oats with flaked oats (or instant oats, which may in fact be the same thing)
Tiny bit of almond extract for the almonds.
People say that roasted unsweetened coconut shavings work just fine in the scondary for coconut porters, so do that. Toast in the oven on paper until lightly browned and dump in the secondary.
Dunno what to tell you about cashews. Too fatty. May have to go without. There are alcohol-based nut extracts of several types you can use for nutty flavors though. Dunno if i've seen cashew extract.
The maple and the brown sugar might get lost in the beer. Use a dark grade B maple syrup and maybe use more of it. Use molasses instead of brown sugar. It doesn't really matter when you add these - flameout perhaps.
Mix the raisins with vodka, mash 'em up, and leave on the counter overnight before adding to secondary. You might reduce the raisin content - alcohol extraction works very well on them.
If cinnamon is something you like in your granola, be careful with it, because alcohol extracts cinnamon flavor very well.
If your granola has banana chips in it, well, banana is a flavor that gets lost in beer. People who have made banana bread ales with real bananas report that you need something like 2 pounds of banana mash per gallon to get the flavor through. Other people are happy with banana-like esters and just ferment warm with a wheat beer yeast.