Arsenal's quickest Premier League goal and the swiftest of the season - surpassing efforts by Robin van Persie - secured Arsene Wenger's side a straightforward win over hapless QPR, who are now without a goal in four games and six hours.
Loic Remy was denied by a fine Wojciech Szczesny save as the Gunners held on for a fifth successive away win saw to move two points clear of Chelsea, having played two games more, and Tottenham, who play at Stamford Bridge on Wednesday.
Walcott, playing in the central role he has long coveted, troubled Rangers throughout and hit the post midway through the first half, but the visitors played well within themselves ahead of matches with relegation-threatened Wigan and Newcastle which will help decide whether they finish in the top four.
The build-up focused on the future of the respective managers as both Wenger and Harry Redknapp confirmed this week they would be staying put.
Frenchman Wenger dismissed suggestions of a departure to Paris St Germain, while Redknapp reaffirmed his commitment to Rangers, insisting he would be a npower Championship boss next term.
Wenger's immediate focus is guiding the Gunners - without Kieran Gibbs due to a slight thigh strain - into the Champions League and they began the match in fifth following Tottenham's win over Southampton.
Arsenal were seeking their first away win over QPR in the Premier League era and struck with the first attack.
Tomas Rosicky crossed towards Aaron Ramsey, who headed down to Mikel Arteta.
Arteta then threaded the ball through a static defence to Walcott, who had ghosted in behind and fired in a shot across goal and under Robert Green.
Walcott's 13th Premier League goal of the season was quicker than Van Persie's effort against Sunderland in October 2011 and the Dutchman's strike for Manchester United against West Ham last November.
The chances of QPR responding to claim a fifth win of the season did not appear good as Arsenal had surrendered just six points from winning positions this term and were one of two teams - alongside champions Manchester United - not to have lost after taking the lead.
Arsenal's intricate play continued, but a QPR defence without the injured Christopher Samba and Jose Bosingwa - omitted from the squad a week after he was seen laughing at the end of the Reading draw - repelled their visitors' efforts.
QPR were also fashioning openings, but the final ball was often lacking as Arsenal survived and Rangers' wait for a goal extended into a sixth hour.
Walcott came close to his second when he breached the defence once more to latch on to a Rosicky pass and saw his shot turned on to the post by Green.
Bobby Zamora, back from suspension as one of four changes, then set-up QPR's best chance of the half, but Park Ji-sung blasted over and then saw another effort blocked.
Szczesny was kept on his toes for much of the first half, but rarely called into action, before holding Tal Ben Haim's long-range strike as QPR finally managed to put an effort on target.
Stephane Mbia fired over and Andros Townsend curled a free-kick wide as Arsenal allowed QPR opportunities.
Townsend was Rangers' most lively player and twice troubled Szczesny early in the second half.
The goalkeeper first had to stretch to claw away a cross before Townsend's 25-yard shot stung his hands.
Monreal was then booked for tugging back the on-loan Spurs winger, but the Gunners managed to deal with the limp threat from Rangers' nine other outfield players.
Shaun Derry, who replaced the ineffective Mbia at the interval, was booked for bringing down Rosicky, after 64 minutes as Arsenal pushed forward, but the Gunners rarely had to exert themselves.
Green parried clear a swerving Santi Cazorla drive from the left channel and then turned a Walcott shot around the post after the forward had wriggled around Ben Haim.
Arsenal continued to threaten and Clint Hill cut out Lukas Podolski's dangerous cross towards Walcott, who then shot straight at Green.
Seven minutes from time, QPR broke, with Zamora crossing for Remy, whose shot on the turn appeared destined for the far corner, only for Szczesny to save at full stretch.
That was as good as it got for QPR as Arsenal saw out