On 5 January 2011, Öztekin signed a deal with Gençlerbirliği for 21 years on a free transfer.

Öztekin played 50 games in 1.5 years and scored 8 league goals, which later attracted bigger clubs to target him in the transfer market.

On 9 August 2014, Öztekin was sold to the Turkish club Galatasaray for a fee of €2.5 million and signed a contract for four years.

On 24 May 2015, he scored a critical goal in the 11th minute against Beşiktaş, which led to the win over Besiktas and securing the 2014–15 Süper Lig title.

On 8 June 2015, Öztekin made his international debut for Turkey in a 4–0 home friendly win against Bulgaria.