Preheat your oven to 400°F (200°C).
Toss the broccoli florets with one tablespoon of olive oil, salt, and pepper on a large baking sheet.
Roast the broccoli for 15-20 minutes until the edges are tender and slightly charred.
While the broccoli roasts, whisk together the remaining tablespoon of olive oil, lemon juice, minced garlic, and dried oregano in a small bowl.
Coat the chicken breast thoroughly with the lemon-herb marinade and season with a pinch of salt and pepper.
Heat a grill or grill pan over medium-high heat and cook the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Remove the chicken from the heat and let it rest for 5 minutes to lock in the juices before slicing.
Warm the pre-cooked quinoa in a small saucepan or microwave if needed.
Plate the fluffy quinoa and roasted broccoli alongside the sliced chicken breast, finishing with an extra squeeze of fresh lemon if desired.