Preheat oven to 400°F and line a large baking sheet with parchment paper.
Dice the chicken breast, red bell pepper, zucchini, and red onion into uniform half-inch pieces to ensure even cooking.
Arrange the diced chicken and vegetables on the prepared baking sheet and toss with half of the olive oil, sea salt, black pepper, and dried oregano.
Roast for 18-20 minutes until the chicken is cooked through and the vegetables are tender with slightly browned edges.
While the tray roasts, combine the dry quinoa with 0.5 cups of water in a small saucepan, bring to a boil, then cover and simmer on low for 15 minutes until fluffy.
In a large mixing bowl, whisk together the remaining olive oil and the fresh lemon juice to create a simple, clean dressing.
Add the cooked quinoa and the roasted chicken and vegetable mixture into the bowl, tossing thoroughly to coat every ingredient in the dressing.
Garnish with finely chopped fresh parsley and serve warm or chilled as a nutritious meal-prep option.