04/12/2012 at 05:45 AM EDT
John Mellencamp and Meg Ryan
are still going strong – and the rocker had his girlfriend's support while working on his latest project: the musical Ghost Brothers of Darkland County
, which he co-wrote with Stephen King and stars American Idol
's Justin Guarini, in Atlanta.
Two days before the show's world premiere, the couple was spotted dining with five other guests at STK Atlanta. Ryan
looked chic in her black maxi dress and black blazer, while Mellencamp was dressed down in a T-shirt, sweater and jeans, says a restaurant rep. – Jennifer Bradley Franklin