Preheat your oven to 400°F and line a large baking sheet with parchment paper.
In a medium bowl, toss the broccoli florets, sliced red bell pepper, and red onion with half of the olive oil, half of the sea salt, and half of the black pepper.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 18 to 20 minutes until tender and slightly charred.
While the vegetables are roasting, pat the chicken breast dry and season both sides evenly with the remaining sea salt, black pepper, dried oregano, and garlic powder.
Heat the remaining olive oil in a heavy-bottomed skillet over medium-high heat until shimmering.
Place the chicken breast in the skillet and sear for 6 to 7 minutes per side, or until the internal temperature reaches 165°F and the outside is golden brown.
Remove the chicken from the skillet and allow it to rest on a cutting board for 3 to 5 minutes to lock in the juices.
Slice the chicken into strips and serve immediately alongside the roasted vegetable medley.