Cut the tops off the bell peppers and remove the seeds and membranes. Lightly brush the exterior with olive oil and place them upright in a baking dish.
In a medium pot, combine the quinoa and vegetable broth. Bring to a boil, then reduce to simmer and cover. Cook for about 15 minutes or until the quinoa is fluffy and the liquid is absorbed.
In a large skillet, heat the olive oil over medium heat. Add the chopped red onion and garlic; sauté for about 5 minutes until they become aromatic and the onion is translucent.
Stir in the cooked quinoa, crumbled feta cheese, cherry tomatoes, black olives, oregano, thyme, salt, and pepper. Mix well until all ingredients are incorporated.
Carefully stuff each prepared bell pepper with the quinoa mixture, packing it tightly.
Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10 minutes, until the peppers are tender and slightly charred.
Once done, take out of the oven and garnish with fresh parsley or dill before serving.