Preheat your oven to 400 degrees F and line a large sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into bite-sized 1-inch cubes and slice the bell pepper into thin strips.
Place the chicken cubes, broccoli florets, and bell pepper strips onto the prepared sheet pan.
Mince the garlic clove and whisk it in a small bowl with the olive oil, dried oregano, sea salt, and black pepper.
Drizzle the herb oil over the chicken and vegetables, tossing everything thoroughly with your hands or tongs to ensure an even coating.
Spread the ingredients out into a single layer so they roast evenly rather than steaming.
Roast in the oven for 18 to 20 minutes, or until the chicken is cooked through and the vegetables are tender-crisp with slightly charred edges.
Remove from the oven and immediately squeeze the juice of the half lemon over the entire pan to brighten the flavors before serving.