Preheat the oven to 400°F.
In a small bowl, mix lemon juice, olive oil, garlic powder, and dried oregano to create the herb marinade.
Coat the chicken breast with the marinade and let it sit for at least 15 minutes to absorb the flavors.
In the meantime, toss broccoli, red bell pepper, and zucchini with a little olive oil, salt, and pepper, then spread them on a baking sheet.
Roast the vegetables in the oven for about 20 minutes, or until they are tender and slightly caramelized.
While the vegetables roast, heat a grill pan or skillet over medium heat and cook the marinated chicken breast for 6-7 minutes per side, or until fully cooked.
Slice the chicken into strips once rested.
Assemble your bowl by placing the cooked quinoa at the base, then topping it with roasted vegetables and sliced lemon herb chicken.
Drizzle any remaining marinade over the top for extra flavor and serve immediately.