Cook ½ cup uncooked quinoa according to package directions; fluff with a fork and set aside.
Position an oven rack about 6 inches below the broiler and preheat the broiler. Use a large oven-safe skillet for the remaining steps.
Over medium heat, melt 1 tablespoon unsalted butter in the oven-safe skillet.
Add ⅓ cup finely chopped red bell pepper, 1 cup roughly chopped artichoke hearts, and 2 cups roughly chopped fresh spinach to the skillet. Cook, stirring occasionally, about 2–3 minutes, until the spinach is wilted and the peppers are softened.
Sprinkle 2 tablespoons all-purpose flour over the vegetables and cook, stirring frequently, about 1–2 minutes to remove the raw flour taste.
Gradually whisk in 1 ¾ cups milk until smooth. Stir in 1 teaspoon chicken bouillon powder, ¾ teaspoon Italian seasoning, ¾ teaspoon onion powder, ½ teaspoon garlic powder, and black pepper to taste.
Continue cooking over medium-low heat, stirring occasionally, until the sauce thickens and becomes creamy, about 3–5 minutes.
Reduce heat to low (or remove from heat briefly) and stir in ¼ cup plain Greek yogurt until combined.
Add 1 ½–2 cups shredded cooked chicken, ¾ cup shredded Italian cheese blend, and the cooked quinoa. Return to low heat if needed and stir until the cheese is melted and the mixture is evenly combined.
In a small bowl, combine ½ cup Panko bread crumbs, ½ teaspoon dried parsley, ½ teaspoon garlic seasoning (or ¼ teaspoon garlic powder), and 1 tablespoon melted butter; stir until the crumbs are evenly coated.
Evenly sprinkle the breadcrumb mixture over the top of the chicken–quinoa mixture in the skillet.
Place the skillet under the preheated broiler and broil 2–4 minutes, watching closely, until the breadcrumbs are golden and toasted.
Remove from the oven, let rest 1–2 minutes, then serve.