Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Pat the chicken breast dry with paper towels and cut into uniform 1-inch pieces to ensure even cooking.
Prepare the vegetables by cutting the broccoli into bite-sized florets, slicing the bell pepper into strips, and slicing the zucchini into half-moons.
In a small glass jar or bowl, whisk together the olive oil, fresh lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Arrange the chicken and all the vegetables on the prepared sheet pan in a single layer.
Pour the lemon-herb dressing over the ingredients and toss with your hands or tongs until everything is thoroughly coated.
Roast in the center of the oven for 18 to 22 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and slightly caramelized.
Remove from the oven and serve immediately, optionally garnished with extra fresh herbs or a squeeze of lemon.