Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Rinse the dry quinoa thoroughly in a fine-mesh strainer under cold running water for 30 seconds to remove the naturally occurring bitter coating called saponin.
In a small saucepan, combine the rinsed quinoa and water; bring the mixture to a rolling boil over medium-high heat.
Once boiling, reduce the heat to low, cover the pot with a tight-fitting lid, and simmer for 15 minutes until the water is fully absorbed.
Remove the quinoa from the heat and let it sit, covered, for 5 minutes to steam, then fluff it gently with a fork to achieve a light texture.
While the quinoa cooks, place the chicken breast, sliced bell peppers, and zucchini on the prepared baking sheet.
Drizzle the chicken and vegetables with olive oil and season evenly with sea salt, black pepper, and garlic powder.
Roast in the oven for 20 to 25 minutes until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly browned.
Slice the roasted chicken into strips and serve it alongside the vegetables over the fluffy quinoa, garnishing with fresh chopped parsley.