Tottenham were second best for long periods on Saturday but Arsenal lacked a cutting edge until Oxlade-Chamberlain was in the right place at the right time to rescue them a point.
Nacer Chadli had put the visitors in front 11 minutes after half-time with his fourth goal in five Premier League matches this term.
Hugo Lloris then saved well from Per Mertesacker to preserve Tottenham's advantage but Oxlade-Chamberlain was alert when the ball dropped to him in the box with 16 minutes left.
Arsenal streamed forward from that point but they could not find a second goal, as they were forced to settle for a fourth draw in six unbeaten Premier League outings this season.
Oxlade-Chamberlain was preferred to Alexis Sanchez on the right flank by Arsenal manager Arsene Wenger, while opposite number Mauricio Pochettino handed Ryan Mason a Premier League debut after the midfielder had impressed during the midweek League Cup win over Nottingham Forest.
Aaron Ramsey gave Lloris some early work in the Tottenham goal after Danny Welbeck had caught Etienne Capoue in possession.
Welbeck was similarly predatory on the halfway line in the 14th minute, dispossessing Jan Vertonghen and racing forward before a last-ditch block from Younes Kaboul denied the England striker.
Lloris showed good positioning when Jack Wilshere thudded a dipping 26th-minute drive into his chest as Arsenal enjoyed a dominant opening, although Mathieu Flamini was forced into the action after an injury to fellow midfielder Mikel Arteta.
Mason was unable to find Emmanuel Adebayor on a rare foray forward from Tottenham, while the former Arsenal striker did not make the most of a 38th-minute opening.
That prompted Tottenham's best spell of the half and, after Lloris had palmed an Oxlade-Chamberlain strike away from the bottom corner, visiting winger Chadli dragged a shot wide on the subsequent 43rd-minute break.
Arsenal were forced into a change in first-half stoppage time, with a hamstring injury to Ramsey seeing Santi Cazorla enter the fray, before Adebayor swivelled to bring a sprawling save from Wojciech Szczesny.
Wilshere - who emerged for the second period despite painfully turning his ankle before half-time - produced a delicate pass to find Mesut Ozil in the Tottenham box, but Lloris was equal to the task once more.
Despite appearing to be off the pace as they did at the start of the first half, Tottenham stunned the Emirates Stadium crowd by taking a 56th-minute lead.
Christian Eriksen muscled Flamini off the ball to find Erik Lamela, who picked out Chadli for an assured finish.
Lloris prevented an almost immediate response by stopping a Mertesacker header on the line from Ozil's free-kick.
Arsenal right-back Calum Chambers nearly scored his first senior goal with a superb 30-yard effort that flew narrowly over the top corner after 72 minutes.
But the home faithful were soon celebrating when Flamini steered the ball across Tottenham's box, where Welbeck failed to turn home but Oxlade-Chamberlain did so emphatically - meaning the visitors' winless Premier League run extended to four matches.
