Preheat oven to 400°F. Line a large baking sheet with a silpat mat or foil and set aside.
In a medium bowl, combine all of the greek marinade ingredients and whisk well. In a separate large bowl, add the potatoes, bell pepper, tomatoes and onion. Pour half the marinade over the veggies and mix well to coat. Set the remaining marinade aside.
Pour the vegetables with the marinade onto the prepared baking sheet and roast in the oven for 15 minutes.
While the veggies are roasting, prep the chicken. Trim any fat from the chicken and either pound the chicken or cut the chicken in half lengthwise so each chicken breast is about ½ inch thick.
Add the prepped chicken to the reserved marinade and toss to coat.
When the veggies are done roasting, remove from the oven and stir well then push the veggies to one side of the baking sheet, making sure the veggies aren’t overlapping. Add the chicken to the other side of the baking sheet then bake for another 15-18 minutes or until the center of the chicken reaches an internal temperature of 165°F.
Broil for 3-5 mins until potatoes are slightly browned and tomatoes shrivel.
Top with kalamata olives, feta cheese and chopped parsley if desired.