Can you put cold stoneware in the oven?

I was going to use mine too. Mine a Rival, has a stoneware insert. It says it can go in the oven, but does not mention temps. The lid can not go in, but I thought I could use heavy foil. I think I'll check their site first for temp info. I found this on the crock pot website. It says that all Crock-Pot slow cooker removable crockery may be used safely in the oven with temperatures up to 400°F without the lid.