According to the UEFA Europa League group stage draw that took place in Monaco today, the Black Eagles were placed in Group L together with Porto, CSKA Sofia and Rapid Wien. 

A total of 48 teams were divided into 12 groups, with each group having 4 teams. Entering the draw from the second seeded pot, Beşiktaş will now battle Porto of Portugal, CSKA Sofia of Bulgaria and Rapid Wien of Austria for a top two spot
Matches to Start on September 16
The group stage will get underway on September 16 and will be concluded with the completion of final matches scheduled for December 15-16. The teams are to play 6 matches each (3 home, 3 away) with the top two sides qualifying for the next round.