Preheat your oven to 400°F.
Slice the zucchini into half-moons, the bell pepper into strips, and the red onion into thick wedges.
On a large rimmed baking sheet, toss the zucchini, peppers, onions, and tomatoes with the first tablespoon of olive oil and half of the salt, pepper, and oregano.
Roast the vegetable medley for 20 minutes until tender and slightly charred at the edges.
While the vegetables roast, season the chicken breast evenly with the remaining salt, pepper, and oregano.
Heat the second tablespoon of olive oil in a large skillet over medium-high heat.
Saute the chicken for 6 to 8 minutes per side until golden brown and the internal temperature reaches 165°F.
Add the minced garlic to the skillet during the final minute of cooking, stirring constantly to prevent burning.
Pour the lemon juice into the skillet to deglaze, scraping up any flavorful browned bits from the bottom.
Serve the chicken alongside the roasted vegetables, garnished with crumbled feta and sliced olives.