Sorry, can't help ya there. I haven't been to Grand Lake yet. What you can do is contact the Army Corps of Engineers and ask them for the locations of the latest brush piles that they set. They keep records of that stuff. Some of it is even online. You also might want to try posting that question on some internet fishing forums. And if yer real cheap, like me, you can check out the paper maps at walmart of the local lakes and they show you some of the larger brush piles that have been set and their location.
On a side note, I don't think I'd eat anything out of Grand Lake. It receives runoff from the Tar Creek Superfund site. No lead and contaminants for me, thank you.