The Premier League side had appeared at risk of elimination when the impressive Nick Blackman gave Reading the lead, but after Roberto Martinez changed his team for the second half the superior quality in Everton's squad inspired victory.
Ross Barkley and Gerard Deulofeu struck after the break as Everton marched through to the last 16.
Manager Martinez had made five changes to his Everton team, which included a first start for £9.5million Argentinian defender Ramiro Funes Mori, and winger Aaron Lennon starting in an unfamiliar position at right-back.
Gareth Barry, Brendan Galloway and Tim Howard were also among the substitutes but Martinez's team still retained a strong appearance, and began with reasonable promise when in the eighth minute Arouna Kone shot wide of the left post from just inside of the area.
Within minutes Reading's Blackman, playing with both a confidence and urgency, produced a classy turn on the edge of the Everton area before shooting and forcing a diving save from goalkeeper Joel Robles.
The forward again threatened when played through in the 22nd minute but despite managing to send a low shot towards goal, he struggled to connect with it as he would have hoped and Robles responded with a routine save before the loose ball was scrambled away.
Reading's pressure was gradually increasing on their flat visitors and, shortly after Aaron Tshibola's 25-yard strike was fumbled wide by Robles, they scored the evening's first goal.
Exposing Lennon's discomfort at full-back, Ola John attacked down the left wing and sent a low cross towards the back post where Blackman, having read his delivery, sent a right-footed effort beyond Robles and into the roof of the net for his seventh goal of the season.
Martinez responded at half-time by reverting to his favoured 4-3-3 formation, introducing Barry to provide cover for his exposed back four, and removing Kone, despite him having outperformed fellow striker Romelu Lukaku.
Galloway soon followed in place of John Stones as Funes Mori switched to central defence, but even though Everton remained open it was they who scored next.
Alex Fernandez could only head Gerard Deulofeu's 62nd-minute corner as far as the tidy but previously quiet Barkley, and the promising midfielder capitalised with a fine demonstration of his technical ability by powerfully shooting first time beyond Ali Al Habsi.
At a time when several senior England midfielders are injured, Barkley's goal, his third in an impressive start to the season, will have further enhanced his international prospects, and it also gave both he and his team-mates greater belief.
The midfielder was soon central to another attack that resulted in a free-kick
It came as a surprise when Deulofeu stood over it, but his direct, curling 30-yard effort, in the 73rd minute, justified him doing so when the ball reached the back of the net, even if Al Habsi will reflect that having got so close he should have produced a save.
Everton responded to their advantage by becoming hesitant under Reading's desire to equalise, but the hosts' willingness to gamble failed to create a truly clear-cut chance.
Source : PA
Source: PA