Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper
Prep the vegetables: Grate the zucchini. No need to squeeze or drain. Give it a quick chop or two so the strings are not very long. Finely chop the ½ cup packed spinach.
Mix the ingredients: In a large mixing bowl, combine the ground chicken, breadcrumbs, grated zucchini, chopped spinach, egg, salt, and garlic powder. Use a rubber spatula or your hands to mix until well combined.
Form the meatballs: Scoop out uniform portions of the mixture (abut 2 tablespoons each) and roll them into balls. If the mixture is sticky, wet your hands slightly to make rolling easier. Place the meatballs evenly spaced on the prepared baking sheet.
Bake: Transfer the meatballs to the preheated oven and bake for 18-22 minutes, or until they are cooked through and lightly golden. I like to give them a shake or flip about halfway through so they don't only brown on one side. The internal temperature should reach 165°F.
Serve & enjoy: These meatballs are so versatile! Serve with your favorite dipping sauce, marinara, or a chinese takeout inspired sauce like the one from this sesame chicken.