Roberto Martinez's side took the lead through Steven Naismith but Colombia star Jackson Martinez finished a fine move shortly before the hour to haul the Portugese side level.
Osman, who has made close to 400 appearances over more than a decade at Everton, almost left his own party the matchwinner but though he met Tony Hibbert's ball into the box, his shot was blocked.
Tim Howard, back after his World Cup heroics with the USA, made a brief appearance before being replaced by Joel Robles just 20 minutes in but neither Blues player was really tested before the break, a Ricardo Quaresma shot from range posing rare threat.
Ross Barkley and Phil Jagielka went close but Naismith broke the deadlock three minutes before half-time when he stroked an Aiden McGeady pass into the bottom corner without breaking stride.
New £28million signing Romelu Lukaku was paraded on the pitch during the interval, while another new face, Bosnia midfielder Mo Besic endeared himself to the crowd with a gutsy challenge at the byline, as well as a thunderous volley.
But the contest ended in a draw after Martinez collected a ball in the box, cut inside and found the far corner (57).
Osman was replaced by young striker Conor McAleny three minutes from time, departing the field to a standing ovation.
Martinez declared himself pleased with his side's performance and though coy on a possible move for Chelsea's Ghana winger Christian Atsu, admitted he remained in the hunt for another fresh face.
"We will keeping working on (transfers) - the squad is not finalised," Martinez told Sky Sports News.
"We're looking for another addition but at the moment the focus is on making sure we are ready to start the season in the best possible way.
"The game was what I expected - Porto are very well drilled with good individuals.
"For us to be able to work on lots of tactical aspects, and see how the youngsters would cope with such demanding opponents, it was very pleasing all round."