Preheat oven to 400F. Spray a large rimmed baking tray with cooking spray.
Whisk together oil, lemon juice, oregano, salt and pepper.
Place chicken in a bowl and pour half the oil mixture on top. Turn chicken to coat well. Marinate 1 to 3 hours in the refrigerator or proceed with recipe.
Place potatoes, zucchini and onion in a large bowl and pour remaining oil mixture on top. Turn vegetables to coat well. Scatter vegetables and garlic on prepared baking tray. Arrange chicken on tray.
Bake 15 minutes. Remove from oven. Scatter cherry tomatoes on top of vegetables. Return to oven and bake 15 to 20 minutes, until chicken is done and vegetables are tender. Serves 6.