Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch cubes and chop the broccoli and red bell pepper into bite-sized pieces.
Place the chicken and vegetables on the prepared baking sheet, drizzle with the extra virgin olive oil, and sprinkle with sea salt, black pepper, garlic powder, and dried oregano.
Toss everything together until well-coated, then spread into a single, even layer to ensure proper roasting.
Roast in the oven for 18-20 minutes, or until the chicken is fully cooked through and the vegetables are tender with slightly caramelized edges.
While the bowl components are roasting, whisk together the tahini and lemon juice in a small bowl, adding a teaspoon of warm water at a time until it reaches a smooth, pourable consistency.
To assemble, place the warm cooked quinoa in a bowl, top with the roasted chicken and vegetables, and finish by drizzling the lemon-tahini sauce over the top.