Preheat the oven to 400°F (200°C). Line a baking sheet and lightly coat with nonstick spray.
In a large mixing bowl, combine the slightly beaten eggs, cooked chopped spinach, chopped yellow onion, minced garlic, grated Parmesan, whole wheat panko, and ground chicken. Mix until evenly combined.
Form the mixture into 1-inch meatballs using your hands or a spoon and place them on the prepared baking sheet, spaced slightly apart.
Bake uncovered for about 20 minutes, or until the meatballs are golden brown and cooked through (internal temperature 165°F / 74°C).
Serve the meatballs over pasta, zoodles, or spaghetti squash as desired.
