Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Toss the broccoli florets with olive oil, salt, and pepper, then spread them on the baking sheet and roast for 15-20 minutes until the edges are crispy.
While broccoli roasts, rinse the quinoa under cold water, then combine it with 1/2 cup water in a small saucepan.
Bring the quinoa to a boil, then reduce heat to low, cover, and simmer for 15 minutes until water is absorbed.
Season the chicken breast with lemon juice, garlic powder, oregano, salt, and pepper.
Heat a grill pan or outdoor grill over medium-high heat and cook the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Fluff the quinoa with a fork and plate it alongside the grilled chicken and roasted broccoli.