Rinse the quinoa under cold water. In a pot, bring the water or vegetable broth to a boil. Add the quinoa, reduce the heat, cover, and let it simmer for about 15 minutes, or until all the liquid is absorbed.
While the quinoa cooks, heat olive oil in a large skillet over medium heat. Add the chopped onion and sauté for 3-4 minutes until softened. Add garlic and cook for another minute.
Add the red bell pepper, zucchini, and broccoli to the skillet. Stir-fry for about 5-7 minutes until the vegetables are tender but still crisp.
Add the cooked quinoa to the skillet and mix everything together. Stir in the soy sauce or tamari and sesame oil. Cook for another 2 minutes, allowing the flavors to combine.
Remove from heat and sprinkle with sesame seeds and fresh herbs, if desired. Serve warm.