Thanks all. I definitely will steam them next time.
I couldn't wait with that huge pan using up all my kitchen. So... I went ahead with the broiler idea.
I warmed the broiler, stuck them in and timed at 3 minute intervals. Oops.
Few of them actually cracked open, so I kept 3 minuting until some of them were ready to open.
I noticed that the hinge side was wide open by then, so I started opening them that way.
The oysters were overcooked.
I saved and strained the pan juices, and have saute'd the onions and celery.
I still have to clean some garlic to add.
I'm debating whether or not to add the actual oysters to the stew. I would hate if it ended up with a scorched taste.