Combine dressing ingredients in a bowl and stir to combine. Place in fridge until ready to use.
Preheat oven to 450 degrees. Line a baking sheet with foil and spray with non-stick spray.
Combine potatoes, olive oil, garlic powder, oregano, salt and pepper in a bowl and stir to coat evenly. Layer potatoes on baking sheet and cook for 30 minutes, flipping halfway through.
To assemble: In 4 bowls, layer spinach, arugula, quinoa, potatoes, beans, red onion, pepperoncini peppers, microgreens and hummus. Top with dressing and serve.