Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Toss the broccoli florets with half of the olive oil, salt, and pepper, then spread them in a single layer on the baking sheet and roast for 20 minutes.
Season the chicken breast with sea salt, black pepper, and garlic powder, then grill over medium-high heat for about 6 minutes per side until the internal temperature reaches 165°F.
While the chicken and broccoli are cooking, ensure your quinoa is prepared according to package instructions using water or a low-sodium vegetable broth.
In a small bowl, whisk together the tahini, lemon juice, and the remaining olive oil to create a smooth dressing, adding a teaspoon of warm water if needed to reach your desired consistency.
Slice the grilled chicken into strips and pit and slice the avocado.
Assemble the bowl by placing the quinoa at the bottom, then topping it with the roasted broccoli, sliced chicken, and avocado.
Drizzle the lemon-tahini dressing over the top and garnish with fresh herbs if desired.