Of course! Usually if you can thaw it first, that is best, but last weekend, I put a partially thawed chicken to brine overnight and it was great. It thawed as it brined. As far as I know, I didn't detect any difference in taste or texture from the usual brining method. Just make sure you give it enough time to fully thaw before you cook it. Brining is the best way to ensure juicy meat when roasted. I love it! Here are some more tips on brining.