Can you cook chicken breasts frozen on the George Foreman Grill?
You can cook chicken breasts from frozen and it is safe, but the quality is arguable.

It would be unsafe if the middle is not fully cooked, or if the cooking process takes over two hours. These two conditions are not hard to meet, but doing so can result that the outer part is dried out. This is no safety concert, but a quality/flavour issue.

To circumvent this, let the breasts thaw in the fridge. Then cook them fully.