Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Chop the broccoli, red bell pepper, and zucchini into uniform bite-sized pieces to ensure even cooking.
Place the vegetables on the baking sheet and toss with half of the olive oil, half of the sea salt, and half of the black pepper.
Roast the vegetables in the oven for 18-20 minutes until they are tender and show slight caramelized charring on the edges.
While the vegetables roast, season both sides of the chicken breast with dried oregano, garlic powder, and the remaining salt and pepper.
Heat the remaining olive oil in a heavy-bottomed skillet or cast-iron pan over medium-high heat.
Place the chicken in the hot skillet and sear for 6-7 minutes per side until the exterior is golden brown and the internal temperature reaches 165°F.
Remove the chicken from the heat and drizzle with fresh lemon juice before serving alongside the roasted vegetable medley.