The Royals made it back-to-back Championship victories by seeing off Posh at the Madejski.
Le Fondre and Robson-Kanu scored within minutes of each other late in the second half to secure all three points for the Berkshire side, after Peterborough had taken a 16th-minute lead through Tommy Rowe.
Simon Church tapped home from close range to level the scores 11 minutes later, but Reading rarely came close to their electrifying best until the introduction of Le Fondre and Robson-Kanu midway through the second period.
And two pieces of individual skill eventually saw of visiting Posh, despite Emile Sinclair's stoppage-time consolation.
Reading moved above the visitors in the league table with the win, and Peterborough continue to wait for their first win in Berkshire in almost 35 years.
The hosts survived an early scare when goalkeeper Adam Federici spilled George Boyd's drive into the path of Rowe, but Alex Pearce blocked Rowe's follow-up.
Reading stuttered in the opening moments, and Lee Tomlin fired narrowly wide for Posh from the edge of the area.
Increasingly it seemed like the visitors would seize the advantage, as Sinclair's low effort was turned around the post by Federici. From the ensuing corner Peterborough took the lead.
Grant McCann floated his cross to the back post and the unmarked Rowe sent a powerful header into the top corner despite the best efforts of Federici.
It was nothing less than the away side deserved for their early dominance, and moments later they should have been two goals to the good.
Sinclair, making the most of a moment of woeful hesitancy within the Reading back four, bore down alone on goal only to shoot wide from 15 yards.
The Madejski Stadium crowd was starting to get anxious and edgy but, with their first attack of any significance, the Royals got themselves back on level terms.
A flurry of corners resulted in Ian Harte crossing from the right, and Jimmy Kebe rose at the back post to nod the ball goalwards, leaving Church with the easiest of tap-ins.
However, despite the strike, Reading could not get a stranglehold on proceedings and the sides went into the break level.
After the interval McCann flashed a shot wide for Posh, Le Fondre headed over from close range for Reading and McCann forced Federici into a decent save low to his right.
Le Fondre then produced the kind of clinical finishing that convinced Reading manager Brian McDermott to sign him from Rotherham in August.
Teed up by Kebe on the edge of the area, the striker fired a sublime curling effort around his marker and beyond Paul Jones into the top corner in the 78th minute.
If that was good, Robson-Kanu's strike just two minutes later was dazzling.
Taking possession near halfway, the Welshman ghosted past two defenders, cantered into the area and produced a deft finish with the outside of his left boot.
Peterborough gave themselves a slither of hope late on, when Sinclair nicked in to round Federici and slide home, but it was too little too late.