In a small bowl, whisk together the lemon juice, minced garlic, and one teaspoon of olive oil to create a marinade.
Place the chicken breast in a shallow dish or bag, coat with the marinade, and let it rest for at least 10 minutes.
Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the broccoli florets with the remaining teaspoon of olive oil, sea salt, and black pepper, then spread them evenly on the baking sheet.
Roast the broccoli for 15 to 20 minutes until the edges are crispy and slightly browned.
While the broccoli is roasting, heat a grill or grill pan over medium-high heat.
Grill the chicken for approximately 6 to 7 minutes per side or until the internal temperature reaches 165°F.
Warm the pre-cooked quinoa and serve it alongside the sliced grilled chicken and roasted broccoli.