It took over half an hour for David Silva to test Buffon in the Italy goal and after Luca Toni had a dangerous header blocked at the other, Silva shot just wide with a second attempt.
Portugal, who only managed 17 goals in their 10 qualifying games, failed to test Barry again after Ronaldo's early shot until the Elephants keeper stopped a weak header from the largely anonymous Liedson after 57 minutes.
As half-time approached, Peter McDonald looped a header towards Celtic keeper Fraser Forster that cleared the bar, then a Grainger corner failed to test the visitors' defence.