Addicks manager Lee Bowyer tried to sign the 28-year-old on loan in January, but a move fell through after Bolton failed to secure a deal for striker Ched Evans.
But Bowyer is now expected to return for Oztumer this summer and attempt to secure him on a permanent deal.
Oztumer began his career at Charlton, but was released at the age of 16 and spent three years playing in Turkey, featuring for Sivasspor and Anadolu Bagcilar.
He returned to England in 2012, joining non-League Dulwich Hamlet, where he went on to score 60 goals in 96 appearances before being picked up by Peterborough and then Walsall
After scoring 32 goals in 95 appearances for the Saddlers, Oztumer joined Bolton last summer but has since seen his first-team chances restricted.
Charlton secured their placed back in England's second tier with a 2-1 play-off final win over Sunderland in May.
Bolton, meanwhile, are preparing for life back in League One following relegation and will begin the campaign on minus 12 points after entering administration.