01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - Prepare quinoa according to package directions. Set aside.
03 - Heat olive oil in a skillet over medium heat. Sauté onion until soft, about 3 to 4 minutes. Add garlic and cook for 1 minute. Add broccoli and sauté until just tender, about 5 minutes for fresh or until heated through for frozen.
04 - In a large bowl, whisk together eggs, milk, sour cream, thyme, paprika, salt, and pepper. Stir in the cooked quinoa, sautéed vegetables, and 3/4 cup of the shredded cheese until evenly combined.
05 - Pour the mixture into the prepared baking dish. Top with the remaining cheese and breadcrumbs if using.
06 - Bake uncovered for 30 to 35 minutes, until bubbly and golden on top. Let rest 5 minutes before serving.