Torquay coach Richard Hancox said of McKoy: "He comes highly recommended.
"He is due to train with us and sign on loan until the end of the season, so he will be eligible for Saturday's FA Cup tie against Southampton.
"He's tall, strong and a capable lad. We've had good reports about him and he played a fair bit for MK Dons last season and was good enough for Cardiff to get hold of him."