two phone, one onsite, one follow-up phone. Mostly is about your past experience and your skillset and what they need. There's a peer-round table session that you can ask any questions for non-evaluation purpose.
I applied online. The process took 2 months. I interviewed at Lawrence Berkeley Lab (Berkeley, CA) in Jan 2016
Interview
The interview last about a whole day. Give a presentation in front of the group members for almost 45 mins including question & answer section. And talk with most group members 1 vs 1 regarding to their research. Have lunch together with some group members.