We were seeded into Group C in today's draw in Monaco.
Besiktas finished third in the Turkish Super Lig in 2013-14 to take their place in the third qualifying round of the Champions League. They beat Feyenoord 5-2 on aggregate before losing out to Arsenal in the play-off, a goalless draw in Istanbul followed by a 1-0 loss at the Emirates on Wednesday night.
Partizan were runners-up by one point in the 2013-14 Serbian SuperLiga to qualify for the second qualifying round of the Champions League.
They enjoyed a 6-1 aggregate win over Havnar Boltfelag of the Faroe Islands before defeat against Bulgarian side Ludogorets Razgrad in the third qualifying round.
Partizan then faced Neftci of Azerbaijan in the Europa League play-off and ran out 5-3 winners over two legs.
Asteras Tripolis finished fifth in the Greek Superleague and went into the end-of-season play-offs. They finished fourth of four teams in the play-offs to take their place in the second qualifying round of this season's Europa League.
Kicking off their European campaign in mid-July, Asteras beat RoPS Rovaniemi of Finland 5-3 in the second qualifying round then Mainz of Germany 3-2 over two legs. They then went through against Maccabi Tel Aviv on away goals after a 3-3 draw on aggregate.
The group match dates are September 18, October 2 and 23, November 6 and 27 and December 11 - as soon as we know who we are playing when, we'll let you know.