Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the broccoli florets with half of the olive oil, salt, and pepper on the prepared baking sheet.
Roast the broccoli for 15-20 minutes until the edges are tender and slightly charred.
While the broccoli roasts, cook the quinoa according to package instructions using water or a low-sodium vegetable broth for extra flavor.
Season the chicken breast evenly with garlic powder, salt, pepper, and a splash of lemon juice.
Heat a grill pan or outdoor grill over medium-high heat and lightly grease with the remaining olive oil.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Remove the chicken from the heat and let it rest for 5 minutes before slicing into strips.
Fluff the cooked quinoa with a fork and plate it alongside the roasted broccoli and grilled chicken.
Drizzle the remaining lemon juice over the chicken and broccoli before serving.