The Old Firm duo secured their spot in the competition proper after play-off wins over Galatasaray and Sarajevo last week - and will now face a number of Thursday/Sunday fixtures going forward.
Steven Gerrard's Light Blues have had five games changed so far with Neil Lennon's Hoops facing four new dates .
The rivals are neck and neck at the top of the table with Gers leading the way by just one point - having played one game more than their title rivals.
Rangers will face Standard Liege, Lech Poznan and Benfica in the group stages after reaching this stage of the competition for the third consecutive season.
Celtic will come up against AC Milan, Lille and Sparta Prague in their section after Odsonne Edouard's strike against Sajajevo in Bosnia secured safe passage to the next stage.