Can I freeze marinated cooked flank steak

I would recommend this depending on how you depend to use it when you thaw it - bring it to room temperature, pat it very dry with paper towels, reheat under your broiler watching it closely. Your meat wont be overdone and you will have a finish as if it had been grilled.

I think as long as it has been cooked you're fine. I wouldn't want to freeze raw steak still being marinated as the marinade will continue to work on the meat, and perhaps make it mushy.