Cook the Quinoa: Rinse quinoa; combine with broth in a saucepan. Bring to a boil, reduce to low, cover, and simmer 15 minutes until absorbed. Remove from heat, keep covered 10 minutes, then fluff.
Roast the Peppers: Preheat oven to 400°F (200°C). Arrange pepper halves cut-side up in a 9×13-inch dish. Drizzle with half the oil. Roast 15–20 minutes until just softened. Set aside.
Build the Aromatics: Heat remaining oil in a large skillet over medium heat. Sauté onion 5–6 minutes until translucent. Add garlic and oregano; cook 1 minute until fragrant.
Create the Filling: Add spinach in batches; cook, stirring, until fully wilted and excess moisture evaporates. Stir in artichokes and chickpeas; cook 2–3 minutes to warm through. Remove from heat; cool 3–5 minutes.
Combine: Fold in quinoa, yogurt, parsley, dill, lemon zest and juice, and black pepper until creamy and cohesive. Taste and adjust seasoning with lemon/pepper as needed.
Assemble and Bake: Spoon filling into pepper halves; mound slightly. Top with feta. Bake 10–15 minutes until filling is hot, feta lightly golden, and peppers are tender but holding shape. Serve immediately.