Bernardo Silva of Manchester City opened the scoring midway through the first half, sweeping the ball home after a low Nuno Mendes cross was deflected into his path.
Portugal then doubled their lead just before the half-hour mark in comical fashion.
There appeared no danger for the Turkey defence following a poor pass by Joao Cancelo aimed at Ronaldo, but Samet Akaydin’s attempted backpass rolled beyond the reach of goalkeeper Altay Bayindir and crossed the line despite the efforts of Zeki Celik to clear.
Turkey never looked like getting back into the game and Portugal got their third goal early in the second half as Ronaldo found himself in on goal but unselfishly squared for Bruno Fernandes to finish.
Having already beaten the Czech Republic 2-1, Portugal are one of only three sides to have a maximum six points from their opening two games and are now certain to win the section even before playing Georgia in Gelsenkirchen on Wednesday.
They therefore know they will play a last-16 tie in Frankfurt on July 1 against one of the best third-place finishers.
“We are first in the group and we can make changes in the next game which for me is very important as there are lots of players in the dressing room who deserve to play,” said Portugal coach Roberto Martinez.
Ronaldo safety concerns
Ronaldo, appearing at his sixth Euros at the age of 39, will become the tournament’s oldest ever goal-scorer if he finds the net in Germany but he failed to add to his competition record tally of 14 here.
The superstar forward, now playing in Saudi Arabia, was also approached for a selfie by several pitch invaders in the second half.
While he enjoyed the attention the first time, posing with a smile for a photograph in the centre circle, he appeared visibly irritated as the number of invaders grew.
Martinez admitted the ease with which so many fans got into the playing area was a concern.
“It is a concern because today we were lucky that the intentions of the fans were good,” he added.
Earlier, Georgia claimed a historic first ever point at a major tournament in a 1-1 draw with the Czechs.
Georges Mikautadze’s penalty late in the first half put Georgia in front but Patrik Schick chested in an equaliser after the break.
A point does little for either side’s hopes of qualification.
Turkey remain second on three points, two ahead of the Czech Republic and Georgia.
De Bruyne inspires Belgium recovery
Belgium’s 1-0 defeat to Slovakia was the major shock of the opening round, but they made the most of a fast start in Cologne to get their tournament back on track.
Youri Tielemans blasted in inside two minutes from Romelu Lukaku’s lay-off to burst Romania’s bubble after their impressive 3-0 win over Ukraine in the opening game in Group E.
Lukaku, who had two goals disallowed against Slovakia, was again denied by the finest of offside calls in a pulsating second half.
Valentin Mihaila and Dennis Man had chances to level for Romania, but Belgium captain Kevin De Bruyne rounded off a fine individual display with the second goal to seal victory 10 minutes from time.
“I’m very relieved that we won the game,” said Belgium boss Domenico Tedesco.
“I think it was possible to score three, four or five goals tonight. It’s great we create these kinds of chances and we need to say patient.”
The group is now fascinatingly poised with all four sides on three points after Ukraine beat Slovakia 2-1 on Friday.
Belgium face Ukraine next, while Romania take on Slovakia with all to play for.
Scotland will aim to reach the knockout stages of a major tournament for the first time on Sunday when they take on Hungary in Stuttgart.
Hosts Germany have already secured their place in the last 16 but can guarantee winning Group A by avoiding defeat against Switzerland.
© Agence France-Presse
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