Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and peel and dice the sweet potato into small, half-inch cubes to ensure they cook through.
Chop the broccoli into small florets and slice the red bell pepper into bite-sized strips.
Place the chicken, sweet potato, broccoli, and bell pepper onto the prepared sheet pan in a single layer.
In a small mixing bowl, whisk together the extra virgin olive oil, minced garlic, lemon juice, lemon zest, dried oregano, sea salt, and black pepper.
Drizzle the lemon-herb dressing over the chicken and vegetables, then use your hands or tongs to toss everything until thoroughly and evenly coated.
Spread the mixture out again, ensuring there is space between the pieces so they roast rather than steam.
Roast in the oven for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are tender and slightly caramelized on the edges.