To quote myself:
I've seen instructions for cooking ratatouille in a crockpot, but what's the point? By the time you've finished sautéeing all the separate ingredients, your ratatouille is about 15 minutes short of being ready to eat!Believe me, mushy ratatouille is not a nice thing, and that's what you'd get if you cooked it in your slow cooker. To retain the freshness of the ingredients, stick to a miminum of cooking.
Reserve your slow cooker for dishes that benefit from a long, slow sojourn at a low heat.