Thawing something from the freezer to cook for dinner has saved us from many a last-minute grocery store run, but what happens if you forget about what you thawed or your plans change? Can you safely throw that meat or poultry back in the freezer to cook another time? You can, but only in one instance!
Kitchen Fact: You can only safely refreeze meat or poultry if it was thawed in the refrigerator.
If you defrosted meat or poultry in the refrigerator, you can refreeze it without cooking it. The quality might suffer from the refreezing process, but it is perfectly safe to eat because the refrigerator method thaws food at a safe, constant low temperature that inhibits rapid bacteria growth.
Other methods of thawing, like the microwave or cold water methods, can thaw food unevenly and some parts might warm up before others and reach a higher temperature. Meat and poultry thawed these ways should be cooked immediately. Once cooked to kill off any bacteria present, they can be safely refrozen.
Kitchen Fact Source: The Big Thaw - Safe Defrosting Methods — for Consumers at USDA.gov