Matthieu Marshall enjoyed his best race of the season to secure an under 20 double at Harwell.
The Oxford City athlete finished fifth overall in the final round of the Oxford Mail League to win the category by 32 points and added the county title at a canter.
Marshall recorded 31mins 4secs for the 8.5km course and held off Banbury Harriers’ Tim Wright (31.06) after a close contest.
Alchester’s Olivia Underhill won the Oxfordshire under 20 ladies’ crown after completing the 6.5km course in 28.59.
But she and Becci Hodgson (White Horse Harriers) had to be content with joint second place in the league competition, which was won by Sophie Fowler (Newbury).
Woodstock Harriers’ James Bolton (vet 40 men) and Oxford City’s Gwyneth Hueter (vet 55 ladies) had won their respective league titles with a round to spare.
The other Oxfordshire club athletes to achieve league titles were Banbury Harriers’ Ros Kelling (vet 45 ladies) and Woodstock’s Bryan Vaughan (vet 60 men).
Kelling won by 46 points, but Vaughan was just one clear of Oxford City’s Stewart Thorp.
City won the Division 1 and 3 men’s titles, with Witney Road Runners taking Division 2.
Newbury (Division 1), Abingdon (Division 2) and Eynsham Road Runners (Division 3) took the ladies’ team honours.
Bolton claimed the Oxfordshire vet 40 title, while White Horse duo Ian Lambourn (vet 50) and Tim Hughes (vet 60) also scooped county victories.
Alchester’s Sarah Rendell was crowned Oxon vet 35 ladies champion, with Kelling and Hueter taking the 45 and 55 honours.
Witney and Abingson were the senior men’s and ladies’ team winners, with Headington Road Runners landing both veterans titles.