Preheat your grill to medium-high heat and your oven to 400°F.
In a small bowl, combine 1 tablespoon of olive oil, lemon juice, garlic powder, salt, and pepper. Rub half of this mixture over the chicken breast.
Grill the chicken breast for about 5-6 minutes per side, or until the internal temperature reaches 165°F. Once done, let it rest for a few minutes before slicing.
While the chicken is grilling, toss the chopped broccoli with the remaining 1 tablespoon of olive oil, salt, and pepper. Spread the broccoli on a baking sheet.
Roast the broccoli in the preheated oven for about 15 minutes, or until tender and slightly crispy around the edges.
Prepare quinoa as per package instructions if not already cooked. Measure out ½ cup for the serving.
Plate the quinoa, top with sliced grilled chicken, and arrange the roasted broccoli on the side. Optionally, drizzle any remaining marinade over the top.
Serve warm and enjoy your balanced, flavorful lunch.