After cautious opening exchanges, it was Ghana who had the first chance in the sixth minute. Ishamel Yartey's left-wing cross was met by Osei, who flicked the ball to an onrushing Adams. But his shot from close range was well saved by Eder Hermoza.
Adams saw his powerful shot from 20 metres denied by the right post in the 21st minute and another blocked in a crowded area four minutes later.
With the Peruvians desperate to soak up the pressure from the Black Starlets, their goalkeeper Hermoza did well to punch away two crucial shots in as many minutes: Enoch Adu's long-range effort in the 38th minute and Osei's glancing header seconds later.
However, Ghana's efforts throughout the first 45 minutes were finally rewarded in stoppage time. Osei broke into the left side of the box before passing the ball to Adams in front of goal. The latter saw his first attempt blocked by Hermoza, but Adams was quick enough to collect the rebound and score his third goal of the tournament.
Ghana began the second half from where they left off in the first, and doubled the lead eight minutes after the interval. Adams fed the ball to the centre of the area with a downward header before Issac Donkor's spectacular overhead kick was denied by the right post. But Osei was there to fire home the rebound and take his tournament tally to five.