Preheat your oven to 400°F (200°C).
Dice the zucchini, red bell pepper, and red onion into uniform bite-sized pieces.
Place the vegetables on a large baking sheet and toss with 0.5 tablespoons of olive oil, half the sea salt, and half the black pepper.
Roast the vegetables in the oven for 20 minutes, or until they are tender and show slight caramelization on the edges.
While the vegetables roast, season the chicken breast evenly with the dried oregano and the remaining salt and pepper.
Heat the remaining 0.5 tablespoons of olive oil in a medium skillet over medium-high heat.
Place the chicken in the skillet and sear for 5 to 7 minutes per side, ensuring the internal temperature reaches 165°F.
Mince the garlic and add it to the skillet during the final minute of cooking to release its fragrance without burning.
Remove the skillet from the heat and drizzle the fresh lemon juice over the chicken.
Plate the pan-seared chicken alongside the roasted vegetable medley and serve immediately.