Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the broccoli florets with half of the olive oil, salt, and pepper, then spread them in a single layer on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are slightly charred and tender.
While the broccoli roasts, whisk together the remaining olive oil, lemon juice, minced garlic, and dried oregano in a small bowl.
Brush the chicken breast with the lemon-garlic marinade and season with a pinch of sea salt.
Grill the chicken over medium-high heat for 6-7 minutes per side, or until the internal temperature reaches 165°F.
Let the chicken rest for 5 minutes before slicing it into strips.
Place the warm quinoa in a bowl, top with the sliced grilled chicken and roasted broccoli, and finish with a sprinkle of crumbled feta cheese.