The actress, 28, and the actor, 35, bonded backstage with John Cameron Mitchell and Sam Rockwell. Seyfried was on hand to support Neil Patrick Harris, her co-star in A Million Ways to Die in the West.
Unlike past romances, Seyfried hasn't discussed her love for Long in detail. "It may be that I'm older, and it may be that social media is everywhere now," she told W in April. "I don't think I was really famous until last year—and I felt like no one paid much attention to what I was doing. That was good. But Les Mis was an international hit, and that changed things. Before, I was a little more anonymous."
Even if Seyfried doesn't want to talk about her boyfriend, one thing's certain: they're both into theater. After all, Long is slated to star in Living on Love at the Williamstown Theatre Festival from July 16-26. Seyfried, meanwhile, recently wrapped production on Fathers and Daughters, co-starring Russell Crowe, Diane Kruger and Aaron Paul.