In a large bowl, combine ground chicken, panko, egg, feta, minced garlic, oregano, parsley, salt, and pepper.
Form the mixture into 1-inch meatballs, making approximately 16-20 total.
Heat olive oil in a large skillet over medium heat and brown meatballs on all sides until the internal temperature reaches 165°F (74°C), then remove and set aside.
In the same skillet, add the dry orzo and toast for 1 minute until fragrant.
Pour in the chicken broth and bring to a simmer; cook, stirring occasionally, until the orzo is tender and the liquid is mostly absorbed, approximately 8 to 10 minutes.
Stir in the fresh baby spinach, lemon juice, lemon zest, and butter until the spinach is wilted and the sauce is emulsified.
Return the meatballs to the skillet, toss gently to combine, and serve immediately.