I applied online and was referred by an employee. I heard back about a week after I applied and was told I would be receiving a phone call for a first round interview. The call was very conversational, no tough questions really. She simply had me walk through my resume and asked why I was interested in Groupon. About a week after the first phone interview, I received an e-mail saying I'd been selected for second round interviews in Chicago. I interviewed with two different employees for thirty minutes each. The first interview included some mildly difficult questions while the second was extremely conversational and laid back.