You previously mentioned bringing them corn. Are you now bringing them proper chicken food? Even free-range chickens do best with a complete chicken food available.
Some chickens really like wet chicken food: just put some in a dish and add water. You could try that. If they do like it, they will probably rush up to gobble it next time. So you could just sit it in the pen, let them rush in, and close the door while they are eating.
Some chickens really like wet chicken food: just put some in a dish and add water. You could try that. If they do like it, they will probably rush up to gobble it next time. So you could just sit it in the pen, let them rush in, and close the door while they are eating.