Last week I carmelized onions (for the first time!) according to Joan N's oven method. http://chowhound.chow.com/topics/3611...
This week I decided to try doing it out on our gas grill. This was also a first time for me as I've always let my husband do the grilling. I set the burners on medium and put a roasting pan of 6 lbs sliced onions (with EVOO, S&P) on the grill and closed the top. After half an hour when I did my first check I realized I had it too high and so put the heat down to low. At the 1 hour check, it looked great--except for a burnt patch on the bottom. So at that point I got a cookie sheet and placed it underneath. The attached picture was at the hour and a half point with the temperature showing around 300 degrees. I cooked them about another 20 minutes and there was quite a bit more burning at the bottom.
Two questions: should I have taken them off at the hour and a half point (pictured), or did they need to get darker? And does anyone have any suggestions on how to avoid the burning on the bottom of the pan? (Have had the same problem roasting potatoes on the grill this way.)
I was able to get enough good carmelized onions out of the deal that I would still do this again on the grill (to keep the house from getting so hot in the summer), but of course I'd like to avoid the burnt bottom. I know now to start with the grill on low and to have the cookie sheet in place from the start, but any other tips would be greatly appreciated. (And just to head anyone off at the pass, no, I am not going to do it the "proper" way of cooking them 5 hours on the stove!)