Oladi, who is training with the team, is looking forward to a five-year contract with the German team, according to his agent.
Schalke 04 coach Felix Magath is satisfied with the performance of the 24-year-old player.
Oladi took part in the La Liga team Deportivo Xerez training in September but could not join the Spanish team due to his lack of necessary documents.
Iranian duo Vahid Hashemian and Ashkan Dejagah have previously worked under Magath in Bayern Munich and Wolfsburg.