If using chicken breasts pound them to 1/2-inch thickness (chicken thighs don't need to be pounded even, skip that step). Dab chicken dry with paper towels. Season with salt, pepper, and oregano on both sides.
Heat 1 Tbsp olive oil in a cast iron skillet or other heavy skillet over medium-high heat. Cook chicken until golden brown on both sides and cooked through , about 5 to 6 minutes per side. Transfer to a cutting board, rest 5 minutes then chop.
Meanwhile in a large mixing bowl toss together bell pepper, cucumber, tomatoes, red onion, avocado, parsley, lemon juice and 2 Tbsp olive oil. Season with salt to taste.
Among six bowls divide cooked quinoa, cooked chicken, and cucumber salad. To each add a dollop of tzatziki and hummus then sprinkle with feta.
*To roast the bell pepper I just char over the flame of a gas stove using metal tongs, turning occasionally until it has some blackened charred spots all over. You can also roast under the oven broiler on a baking sheet, turning occasionally. Keep a close eye on it while roasting on stovetop or in oven. Let it cool a bit before chopping.
Nutrition estimate based on using chicken breasts. Chicken thighs will increase calorie and fat count.