Applied online, rejected within a week. Emailed me a few weeks later saying they were reassessing their hiring needs and wanted to set up an interview. Like others I've talked to, OW takes a while for the interview process during off cycle hiring due to scheduling consultants for interviews. Again like others, there was an online math skills test, 30 questions, 20 min, of algebra and stat questions. I only answered 6 that I knew were correct (1 point for right answer, -1 for wrong, can skip as many as you want) and still got it. 1st phone interview, 1 30min case study, no fit/resume questions with a Senior Associate. It was as I expected, initially I thought it was difficult but it was my very first case interview. They offer feedback whether you pass or not which is great. I heard back within a day. 2nd phone interview, 1 30 min case study, no fit/resume questions with a Senior Consultant. This one was definitely harder, more of a discussion. I didn't get to the conclusion but she passed me because I had "great ideas" and she felt I had good business acumen. Heard back within a few hours, again feedback was given. Final round in late June, fly you up all expenses paid. Took a while to schedule due to consultants availabilities and they only do them on Fridays. 4 45 min interviews, 3 case and 1 fit in random order with Director, Associate, Sr Consultant and Consultant (fit). Cases were more difficult and the Director applied stress which is what tripped me up. Found out within a few hours that I got no offer. Aside from having to wait so long, I thought it was a great interview experience and everyone I spoke to seemed extremely smart and talented. OW is also considered one of the top 20 hardest firms to interview for http://www.businessinsider.com/companies-hardest-interview-process-2011-6