Whisk together one teaspoon of olive oil, lemon juice, minced garlic, salt, and pepper in a small bowl.
Place the chicken breast in the marinade and let it sit for at least fifteen 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 and a pinch of salt, then spread them on the baking sheet.
Roast the broccoli for fifteen to twenty minutes until the edges are tender and slightly charred.
While the broccoli roasts, heat a grill pan or outdoor grill over medium-high heat.
Grill the chicken for five to seven minutes per side until the internal temperature reaches 165°F.
Let the chicken rest for five minutes before slicing.
Serve the sliced chicken over the warm quinoa with the roasted broccoli on the side.