No interview, really. Just general questions about your work history, as well as salary preferences, and then they call you whenever there's a contract that matches your skillset. Make sure you like your recruiter though.
I applied to one of their job postings and received a call from a recruiter a few days after. She simply asked for my work history and experience, and pay requirements. Then she called back about a month later once a contract opened that fit what I was looking for.