Oliver Wyman had 2 interview rounds. The first round involved one case interview and one behavioral interview. My case interview with OW was the first case interview of my life, and I think that worked in my favor. People tend to over-prepare for cases and that's not good because if you over-prepare, you tend to think only in terms of the frameworks and cases that you've read about and do not apply any creativity or original thinking. The behavioral interview was a standard resume-based interview. For this one, make sure you know your resume really well and that you're not lying about anything on your resume. The second round was on campus. It involved 4 case interviews (back-to-back) and one behavioral interview. Pretty much the same advice applies here but I learned something very important about my resume here. On your resume, make sure that you have at least one thing that you are extremely passionate about (or that makes you really stand out). During one of my case interviews, the partner who was interviewing me saw a research project on my resume and he was so intrigued by it that we ended up talking about the project for a good 10-15 minutes (even though we only had 30 minutes in total for the case). It was during the second round interviews that I fell in love with OW. I loved each one of my interviewers and we also got the chance to speak with a lot of fresh recruits. They were all very nice and polite. Oliver Wyman is prestigious, yet it's not as big as McKinsey or BCG. And I like the sort of small company feel to it.

It took a whole day -two rounds. All case interviews with follow-up questions. Standard questions. The second round is with two partners. I spent the whole section chatting with one partner.