In a large skillet, heat olive oil over medium-high heat. Add the onion and garlic. Sauté until the onions are softened, about 3 minutes. Add the ground chicken, dried oregano, salt and black pepper. Sauté until the chicken is cooked and lightly browned, about 5 to 6 minutes. Add the spinach and cook until wilted, about 2 minutes. Add 1 cup of the tomato sauce, the artichoke hearts, the rice and the sun-dried tomatoes.
Remove from heat and stir in 1/2 cup of feta cheese.