How old do you have to be to cook on the grill?

It honestly doesn't matter. I would say that maybe the best time to start is 13, but smaller kids can help around the kitchen under parental supervision.

I started cooking on my own when I was 8 or 9, maybe younger. Kids love to help Mom or Big Sister, and can be started with supervision as early as two or three (for helping add premeasured ingredients or stirring).