Heat the oven to 425°F. Set a large rimmed sheet pan on the counter and line it with parchment paper if you want easier cleanup.

Put the broccoli, mini sweet peppers, and red onion into a large bowl.

Add 2 tablespoons olive oil, 1 teaspoon kosher salt, and 1/4 teaspoon black pepper to the bowl of vegetables.

Toss the vegetables until they are evenly coated with oil and seasoning.

Spread the vegetables on the sheet pan in a single layer, leaving an open space through the middle for the meatballs.

Use the same bowl for the chicken mixture. Add the ground chicken, Parmesan, panko, lemon zest, dried oregano, and garlic powder to the bowl.

Crack the egg into the bowl with the chicken mixture.

Add the remaining 1/2 teaspoon kosher salt and remaining 1/4 teaspoon black pepper to the bowl.

Mix the chicken mixture gently with a fork or your hands until it is evenly combined. Stop when everything looks mixed so the meatballs do not get tough.

Wet your hands lightly with water and shape the chicken mixture into 12 meatballs, each about 2 inches wide.

Place the meatballs in the open space on the sheet pan. Leave a little room between them so the hot air can move around them.

Drizzle the remaining 1 tablespoon olive oil over the meatballs.