I had a written interview at BCG in the decision round just a couple of weeks back.
They put you into a room and give you a memo along with a bundle of papers. The memo is an e-mail from your senior colleague, basically saying that a new client has appeared who wants data presented tomorrow. The senior colleague is a bit too busy and needs you to summarise the data and send it to him/her asap.
The bundle is a body of around 30 slides that has a lot of info about the client. Some useful, some not.
Your goal is to distil what is important from all of this and use it to formulate an executive summary.
You won't have to 'present' in front of an audience but will discuss it with the Partner/Principal along with your rationale.
Look out for quant - if you're not calculating, you're doing something wrong.
My advice would be to begin writing the executive summary first, and fill it out as you find relevant data. WRITE DOWN YOUR RATIONALE cos under pressure you won't remember it.
Out of the 30 slides, only around 10 of mine were useful. The Principal then scrutinised my decision-making process and rationale.
It won't be easy so be sure to budget your time and keep an eye on the clock!