Cook the base: Prepare brown rice or quinoa according to package directions. Fluff and set aside.
Prep the veggies: Steam or roast broccoli and bell peppers until crisp-tender.
Season lightly with salt and a drizzle of olive oil.
Make the meatball mixture: In a large bowl, combine ground chicken, onion, garlic, panko, egg, parsley, oregano, salt, pepper, and smoked paprika. Mix gently with a fork or your hands until just combined. Avoid overmixing.
Form the meatballs: With damp hands or a scoop, form 18–20 meatballs, about 1.5 tablespoons each.
Place on a plate or sheet pan.
Cook on the stovetop (option 1): Heat 1 tablespoon olive oil in a large nonstick skillet over medium heat. Add meatballs in a single layer, not crowding the pan. Sear 2–3 minutes per side until browned, then cover and cook another 4–6 minutes, turning once, until cooked through.
Internal temp should reach 165°F (74°C).
Or bake (option 2): Preheat oven to 425°F (220°C). Line a sheet pan with parchment. Lightly brush or spray meatballs with oil.
Bake 12–15 minutes, turning once, until browned and at 165°F (74°C).
Make the yogurt herb sauce: Stir together Greek yogurt, lemon juice, zest, olive oil, garlic, dill or parsley, salt, and pepper. Adjust lemon and salt to taste.
Assemble the bowls: Divide rice or quinoa among bowls. Top with meatballs, cooked veggies, tomatoes, and cucumber.
Add avocado if using. Spoon over the yogurt sauce and finish with a squeeze of lemon.