Add the butter to a large deep pot on medium high heat until melted.
Add the chicken thighs and cook for 4-5 minutes on one side. Sprinkle ground black pepper on top of each chicken thigh, flip and cook the other side for another 4-5 minutes or until each side is browned on the outside. Remove each chicken thigh and place them on a plate on the side for now.
There should still be some melted butter in the pot. Still at medium heat, add the onion and garlic and cook for 2-3 minutes or until they become fragrant.
Pour in the dry orzo and stir well, lightly toasting it for about 2-3 minutes.
Add the chicken broth/stock, chopped red bell pepper, basil and oregano. Stir, making sure the orzo doesn't stick to the bottom of the pot.
Add the chicken thighs back in to the orzo and broth mixture, spreading them out evenly. Cover the pot with the lid, bring to a boil and then reduce to a simmer. Cook for 15 minutes (stirring every 5 minutes to make sure the orzo doesn’t stick to the bottom) or until the orzo has soaked up the liquid and the chicken has cooked to an internal temperature of 165℉ (73.9℃).
Add the fresh spinach, stir and continue to cook on low for another 3-5 minutes so the spinach can wilt.
Serve immediately with a sprinkle of feta and fresh basil or parsley. Season with salt and pepper and enjoy!