Preheat your oven to 400°F. In a small bowl, whisk together lemon juice, olive oil, minced garlic, and chopped fresh herbs.
Place the chicken breast on a cutting board and pound it slightly if needed for even cooking. Brush both sides generously with the lemon-herb mixture and let it marinate for 10-15 minutes.
Meanwhile, chop your choice of vegetables (such as bell pepper, zucchini, and red onion) into bite-sized pieces. Toss them with a drizzle of olive oil, salt, and pepper.
Spread the vegetables on a baking sheet lined with parchment paper and roast in the preheated 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-high heat. Cook the marinated chicken for approximately 5-6 minutes per side or until the internal temperature reaches 165°F.
Prepare the quinoa by warming the pre-cooked quinoa or cooking according to package instructions if using raw quinoa.
Assemble the bowl by layering the cooked quinoa at the base, topping it with sliced lemon-herb chicken, and arranging the roasted vegetables around the bowl.
Drizzle any remaining lemon-herb dressing over the bowl, garnish with extra herbs if desired, and serve immediately.