Preheat your oven to 400°F and prepare a baking sheet with parchment paper.
Rinse the quinoa in a fine-mesh strainer, then combine with 2/3 cup water in a small pot and bring to a boil.
Reduce heat to low, cover, and simmer the quinoa for 15 minutes until water is absorbed; fluff with a fork.
Toss the broccoli florets with 1 tablespoon of olive oil, salt, and pepper on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are slightly charred and tender.
While broccoli roasts, season the chicken breast with lemon juice, garlic powder, oregano, salt, and pepper.
Heat the remaining 1 tablespoon of olive oil in a grill pan or skillet over medium-high heat.
Grill the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
Slice the chicken and serve it over the fluffy quinoa alongside the roasted broccoli.