Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the broccoli florets with one teaspoon of olive oil, sea salt, and black pepper, then spread them in a single layer on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are tender and slightly charred.
Season the chicken breast with garlic powder, salt, pepper, and half of the lemon juice.
Heat a grill pan or outdoor grill over medium-high heat and lightly coat with the remaining teaspoon of olive oil.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F.
While the chicken rests, fluff your pre-cooked quinoa and place it in a serving bowl.
Slice the grilled chicken and arrange it over the quinoa alongside the roasted broccoli.
Drizzle the remaining lemon juice over the entire dish before serving.