Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Peel the sweet potato and dice it into 1/2-inch cubes, then chop the bell peppers into bite-sized pieces.
Cut the chicken breast into even 1-inch strips to ensure they cook at the same rate as the vegetables.
In a small mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper to create the marinade.
Place the chicken strips, sweet potato cubes, broccoli florets, and bell peppers onto the prepared sheet pan.
Pour the lemon-herb marinade over the ingredients and toss thoroughly with your hands or tongs to ensure every piece is well-coated.
Spread everything out into a single, even layer, making sure not to overcrowd the pan so the vegetables roast rather than steam.
Bake for 20 to 25 minutes, or until the chicken is cooked through and the sweet potatoes are fork-tender and slightly caramelized.