Realized I didn't cook the green beans (frozen) in my green bean casserole. Can I just cook my casserole longer in the oven?

Oh, well then you should be just fine! Happy Thanksgiving!

Is everything already mixed together? What I'd worry about here is water from the defrosting beans making your casserole a bit too watery. The beans will cook if you leave them in the oven longer, definitely, but if there's a way to disassemble and defrost and then carry on, I would do that!