I've been doing mushroom packets lately and love them. I just get a mix of mushrooms (about a pound -- 3 different 5 oz. containers). I toss with salt, pepper, ground rosemary, and 3 tbs of olive oil. Divide it in two onto two parchment paper lined foil squares, then put a crushed garlic clove on each and seal the packets. Cook on the grill for 20 minutes.
I got it off the internet, but it works.