Onoura stayed with The Stags until Gillingham paid £25,000 for him in August 1996. It was at Priestfield Stadium where Onuora's goal scoring ability started to show, as he notched himself a tally of just under 30 goals in an 18-month stay with the club, before the Gills cashed in on their big front man by selling him to Swindon Town in March 1998. More goal scoring success was on the cards and he remained at the club until he secured a move back to Gillingham in January 2000, following a short loan spell.