Preheat your oven to 400°F and prepare a baking sheet with parchment paper.
In a small bowl, whisk together the lemon juice, minced garlic, and one teaspoon of olive oil.
Place the chicken breast in a shallow dish, coat with the marinade, and let sit for 10 minutes.
Toss the broccoli florets with the remaining teaspoon of olive oil and a pinch of salt on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are tender and slightly browned.
While the broccoli roasts, heat a grill pan or outdoor grill over medium-high heat.
Grill the chicken for 6-7 minutes per side or until the internal temperature reaches 165°F.
Fluff the pre-cooked quinoa with a fork and place it in a bowl.
Slice the grilled chicken and serve alongside the roasted broccoli over the bed of quinoa.