In a large mixing bowl, combine ground chicken, egg, breadcrumbs, crumbled feta, chopped parsley, dried oregano, minced garlic, lemon zest, salt, and black pepper. Mix everything gently by hand until the ingredients are well incorporated—take care not to overmix, as this can make the meatballs tough.
Shape the mixture into evenly sized meatballs, about 1½ inches in diameter, using a small scoop or your hands. You should end up with approximately 16 to 20 meatballs.
In a large nonstick skillet, heat the olive oil over medium heat. Once hot, add the meatballs in a single layer, working in batches if needed to avoid overcrowding the pan.
Cook for 4–5 minutes per side, turning as needed, until the meatballs are golden brown all over and fully cooked through (they should reach an internal temperature of 165°F). Once done, transfer the meatballs to a plate and set aside.