What is it about this group/hospital that makes you want to be a part of it?

You must assume the interviewer thinks his or her hospital or group is absolutely wonderful...or potentially wonderful with the addition of the right person. You can stroke the corporate ego and begin endearing yourself to the interviewer by invoking the Mission Statement and/or Vision of the hospital or group. Most hospitals will have these, prominently displayed on the landing pages of their websites; they are brief and easy to imbue into your interview strategy. You can tell the interviewer that you find those values you saw in the Mission Statement and/or Vision Statement align with your personal views of how you want to lead your professional life.
Don't actually refer to the Mission Statement and Vision when you answer; just state that you find this group's values align with yours, and you can paraphrase the ones you saw displayed.