Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Place the broccoli florets, bell pepper slices, and red onion wedges on the baking sheet.
Drizzle the vegetables with half of the olive oil and season with half of the sea salt and black pepper, tossing to coat evenly.
Roast the vegetables in the oven for 15-20 minutes until they are tender and show slight charred edges.
While the vegetables roast, season the chicken breast on both sides with the garlic powder, dried oregano, and the remaining salt and pepper.
Heat the remaining olive oil in a heavy-bottomed skillet over medium-high heat.
Add the chicken to the skillet and sear for 6-7 minutes per side, or until the exterior is golden brown and the internal temperature reaches 165°F.
Remove the chicken from the pan and let it rest for 3 minutes before slicing.
Plate the chicken alongside the roasted vegetables and finish with a fresh squeeze of lemon juice over everything.