I applied online. The process took 2 days. I interviewed at QVARTZ (Oslo) in Sept 2018
Interview
First round: Personal interview and numerical tests
Second round: Two case interviews one on one with a consultant
Third round: Three case interviews, one group case and two cases with different partners
I applied online. I interviewed at QVARTZ in Mar 2019
Interview
First round: 1 HR interview
Second round: 2 to 3 case interviews
Final round: 3 partner interviews
In between the interviews you will also get the opportunity to meet with consultants for a "life at QVARTZ" session, where you will have a casual chat and ask about anything (it's not a part of the interviews).
Hamburg/Germany. Interview with senior consultant about motivation and personal fit questions, at the end 1 case study (how many gas stations are in the US?). Followed in the second round by two partner interviews with the same structure as the first interview. After the interviews I got standard feedback. This was disappointing for me, since QVARTZ markets itself to be distinct from other cunsultancies, but is in fact nothing else. Either give no feedback or be honest!