Rinse the quinoa under cold water in a fine mesh strainer to remove any bitterness.
In a medium pot, combine the rinsed quinoa and vegetable broth. Bring to a boil, then reduce heat to low, cover, and simmer for about 15 minutes, or until quinoa is fluffy and liquid is absorbed. Remove from heat and set aside.
While the quinoa is cooking, heat olive oil in a large skillet or wok over medium-high heat.
Add the minced garlic and sauté for about 30 seconds until fragrant.
Add the chopped red bell pepper, broccoli florets, sliced carrots, and chopped zucchini to the skillet. Stir-fry for about 7-10 minutes, until the vegetables are tender-crisp.
Once the vegetables are cooked, add the cooked quinoa to the skillet, along with the soy sauce, sesame oil, salt, and pepper. Mix well to combine all ingredients thoroughly.
Cook for an additional 2-3 minutes to warm everything through.
Serve hot, garnished with chopped green onions and optional sesame seeds.