An injury-time strike from Luke Ricketts finally broke the stubborn resistance of neighbours Chinnor as Thame United progressed to the next round of the FA Vase.
Thame have been drawn away to Wessex League Premier Division side Alresford Town in the second round, which will be played on November 22.
In front of one of the largest crowds of the day – 283 – United were met with a side who displayed some neat passing football as Chinnor enjoyed the bulk of the play in the first 30 minutes although chances were at premium at both ends.
The first real opening came United’s way when Stacey Field crossed for Ben Gray, but his header was off target, while Chinnor’s Craig Faulconbridge also headed wide.
The visitors then took a shock lead when Faulconbridge converted a penalty.
United were struggling to find their rhythm, but they did manage to pull level before half-time when a long throw from Matt Hall was flicked on by Ellis Hercules and beyond goalkeeper Ben Taunton into the far corner of the goal.
Thame improved after the break with Ben Gray and Adam Morris both going close, while Dan Jones was thwarted by Taunton as the home side strived to find a winner.
Just as the game looked to be heading for extra-time, a perfect through ball from Ollie Lynch was controlled by Ricketts, who placed the ball wide of Taunton to spark scenes of jubilation on and off the field.
On Tuesday, United continued their good form with a fifth straight league victory as they beat Holyport 2-1.
The visitors struck first when Andy Vine placed his effort beyond Cockerill in the Thame goal, but United responded through Ellis Hercules’s goal before Dan Jones scored the winner to take Thame up to fifth in the Hellenic Premier Division.
United visit second bottom Shrivenham this Saturday.