Mike Wedderburn took 6-59, but his Banbury Twenty 2nd side were unable to force the win at home to strugglers Chearsley that would have propelled them to the top of the Division 4 table.
Cumnor captain Carl Thompson took 5-55 to bowl his side to within one wicket of victory over leaders Aston Rowant and a return to the top of Division 1.
Abingdon Vale left-arm seamer Danny Hartley took 8-14 in a devastating spell to re-ignite his side's promotion push in Division 2 and leave opponents Tiddington in the relegation zone.
Banbury Twenty 2nd are back on course for promotion from Division 4 after they beat Buckingham Town 2nd by five wickets and so leapfrog them into the top two.