Voltaggio was a fan favorite on the reality show. He competed against his brother and won during the finale with a four-course menu that included dashi-glazed rockfish, fennel-scented squab breast and butternut squash brûlée.
He recently started his own restaurant, Ink, on Melrose Avenue in Los Angeles.
Voltaggio is one of a number of chefs showing off their culinary chops at this year's fair.
"Top Chef Masters" star Rick Moonen will be serving sustainable seafood Aug. 11.