Preheat oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
In a large mixing bowl, combine the ground chicken, ricotta, chopped spinach, breadcrumbs, Parmesan, egg, garlic, oregano, salt, pepper, and lemon zest.
Mix ingredients by hand until just incorporated, being careful not to overwork the meat to maintain a light texture.
Scoop approximately 2 tablespoons of the mixture and roll into 1.5-inch balls.
Arrange the meatballs on the prepared baking sheet, spaced at least 1 inch apart.
Bake for 20 to 25 minutes or until the internal temperature reaches 165°F (74°C) using an instant-read thermometer.
Remove from oven and allow the meatballs to rest for 5 minutes before serving.