How to grill portabello mushrooms properly Recently my girlfriend and I tried grilling (over an open flame, like BBQ) some portabello mushrooms for burgers.

We failed miserably :( The mushrooms were soggy and raw at first. After grilling them for a while, they were dry on the outside and a bit raw inside. How can I grill them so that they are cooked evenly throughout, without being too soggy or too dry?

I read this post, but I am particularly interested in grilling of mushrooms.
I have found marinating in some sort of olive oil/vinegar type of liquid for about an hour ahead works well.  They feel a little soggy/slippery when you put them on the grill but firm up right away and taste pretty good.

Key is to make sure your fire is hot and direct (don't "smoke" them) - I'd say 350 degrees or so - and pause a moment to ensure the grate is hot as well.  Then I would take them off as soon as you start seeing the grill marks on both sides.  Like 1 minute per side. I personally use equal parts Olive Oil and Red Balsamic.  Sometimes I have also used Worcestershire and it makes them taste even more like a "burger".