Boa tarde.
Segue codigo para reschedule do

def rescheduler = {
ApplicationContext ctx = (ApplicationContext)ApplicationHolder.getApplication().getMainContext();
def quartzScheduler = ctx.getBean("quartzScheduler")


def dfm = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date dt = dfm.parse("2011-07-27 14:23:00");


def trigger = quartzScheduler.getTrigger("CobrancaFupJob", "GRAILS_JOBS")
trigger.repeatInterval = 60000
trigger.startTime = dt

Date nextFireTime=quartzScheduler.rescheduleJob(trigger.name, trigger.group, trigger)

println "Next Fire Time : ${nextFireTime}"


render "teste"

}