Yes you can but it will take a lot longer to cook and all the water/juices that come out as its defrosting will end up in the casserole.
I would defrost it first. If you don't have long to defrost it i suggest if you have a microwave put it on defrost in there for 10 minutes then check on it and put back on for 5 minutes check after each 5 minutes, or if you don't have a microwave pour some hot water into a bowl/tray/something big enough for the chicken to go in and let it defrost like that.