Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Chop the broccoli into bite-sized florets, slice the red bell pepper into thin strips, and roughly dice the red onion.
Place the vegetables on the prepared baking sheet and toss with 0.5 tbsp of olive oil, 0.125 tsp sea salt, and 0.125 tsp black pepper.
Spread the vegetables in a single layer and roast for 18-20 minutes until they are tender and the edges are slightly caramelized.
While the vegetables are roasting, season the chicken breast on both sides with the garlic powder, dried oregano, and the remaining salt and pepper.
Heat the remaining 0.5 tbsp of olive oil in a heavy skillet over medium-high heat until shimmering.
Place the chicken in the pan and sear for 6-7 minutes per side without moving it, until golden brown and the internal temperature reaches 165°F.
Remove the chicken from the pan and let it rest for 3 minutes before serving it alongside the hot roasted vegetable medley.