In a small bowl, combine the olive oil, lemon juice, minced garlic, salt, and pepper to create the marinade.
Place the chicken breast in a shallow dish and pour the marinade over it, ensuring even coverage. Let it marinate for at least 15-20 minutes.
Preheat the grill to medium-high heat.
Grill the chicken breast for about 6-7 minutes per side or until it reaches an internal temperature of 165°F.
Meanwhile, preheat your oven to 425°F for roasting the broccoli.
Toss the chopped broccoli with a small drizzle of olive oil (if desired), salt, and pepper, and spread it out on a baking sheet.
Roast the broccoli in the preheated oven for 15-20 minutes, until the edges are slightly crispy and tender.
Serve the grilled chicken breast alongside the roasted broccoli, and enjoy your flavorful, balanced lunch.