Preheat oven to 400ºF. Line a baking sheet with parchment paper.
Combine oil, lemon juice, garlic, herbs, salt and pepper. Whisk and set aside.
Chop veggies.
Place Brussels sprouts, potatoes, peppers, onions, artichoke hearts on the sheet pan. Pour ⅔ of the vinaigrette over veggies and toss veggies to coat. Make sure all pieces are coated.
Move veggies around to make spaces for the chicken thighs. Place chicken on the pan. Top each chicken thigh with the remaining vinaigrette, then top chicken with lemon slices.
Transfer pan to the oven and bake for 15 minutes. After 15 minutes, remove from oven and add tomatoes, kalamata olives and toss veggies. Place back into the oven.
Bake for an additional 5-7 minutes or until chicken is cooked through. The time will depend on the thickness of the chicken. To ensure chicken is done, you could also use a meat thermometer. Once thermometer reaches 165ºF, remove pan from the oven. OR to crisp veggies up slightly, turn oven to broil and broil for 1 minute before removing from oven. Watch closely.
While chicken and veggies are in the oven, make the Paleo Tzatziki Sauce. This is optional but highly recommended!