Andre Villas-Boas oversaw his first triumph as Tottenham boss with his side producing a very attacking display which could have seen one or two more goals on the scoresheet.
Royals keeper Alex McCarthy, who had been preferred to number one Adam Federici, came up with a vital double save inside five minutes to deny Gylfi Sigurdssonâ€™s header and then Jan Vertonghenâ€™s follow-up.
In the 18th minute, Defoe opened the scoring after Sigurdsson released Aaron Lennon down the right with the winger cutting back for the England striker to tuck home past a diving McCarthy.
Defoe almost had a second five minutes later when he latched on to Sandroâ€™s ball with great control but hit his outside foot attempt wide of the mark with the Royals gloveman well-beaten.
A second goal for Tottenham again almost came when Premier League debutant McCarthy gifted the ball to a dangerous Defoe who supplied Sigurdsson but the former Reading man had his effort cleared off the line by Alex Pearce.
The second half was even more of a problem for Brian McDermottâ€™s outfit with Bale coming close with his 58th minute shot from range before the Welshman made it 2-0 with just under 20 minutes remaining when he got his right foot to Kyle Walkerâ€™s cross from the right to bobble it past McCarthy.
A few minutes later and the contest was essentially wrapped up through Defoe, who in Tottenham's horrible grey and black away kit, took possession in midfield before advancing into the area to slot home a left-footer across his body and in for his third of the season.
Reading managed to net a consolation goal in the last minute of regular time when Adam Le Fondre crossed for substitute Robson-Kanu to finish at the back post with a clever sliding volley but in the end it was nowhere near enough to take anything away from Tottenhamâ€™s performance.
The win has the North Londoners sitting 10th on the table with five points from four outings as Reading find themselves second bottom with just a draw from their three fixtures thus far.
Madejski Stadium, Reading â€“ 24,160
Yellow cards: REA - nil
TOT - Jermain Defoe 90+3â€™