Pat the chicken breast dry with paper towels and season both sides evenly with sea salt, black pepper, and dried oregano.
Heat a large skillet over medium-high heat and add half of the olive oil, swirling to coat the pan.
Place the chicken in the skillet and sear for 5-7 minutes per side until the exterior is golden and the internal temperature reaches 165°F.
Remove the chicken from the pan and set aside to rest on a plate.
In the same skillet, add the remaining olive oil along with the sliced red onion, zucchini, and bell peppers.
Sauté the vegetables for 5-6 minutes, stirring frequently, until they are crisp-tender and slightly caramelized.
Add the minced garlic to the vegetables and cook for an additional 60 seconds until fragrant.
Return the chicken to the pan, drizzle everything with fresh lemon juice, and toss gently before serving.