I applied online for the Madrid Offices and the process took 4 weeks. It consisted of an Assessment Centre and 3 additional interviews.
The AC consisted in 3 exams and one group dynamic. The exams were fairly easy, of mathematics, reading and english, which honestly it was insult, far too easy. After the exams they required us to pitch a business idea in 5 minutes with the only constraint that it had to be e-commerce. After everyone presented their idea we had to argue between the assistants (around 10) which was the best idea and then develop a business plan for it. Since it was in Spain, everything was in Spanish, but for like 10 mins they require that you only speak English, so be prepared for it.
The next round was the HR interview. Basically study your CV and have prepared the typical questions, Why Consulting? Why Management Solutions? Why you?. After it, I interviewed with a Manager where he had some fit questions and later on he started asking more technical questions but no cases at all. The final round was with the Partner, which was the most difficult one for me, very very technical, but in the end you just have to be calm and be yourself! After a week they called me to land the offer.
Really liked their recruitment process.