Using paper towels, squeeze out any excess liquid in spinach.
In a medium bowl combine spinach, cream cheese for cooking, yogurt, mayonnaise, 3/4 cup of the cheese, the olives, 2 tablespoons of the green onions, the pesto, and pepper. Transfer spinach mixture to a 1-1/2-quart slow cooker. Sprinkle mixture with the remaining 1/4 cup cheese.
Cover and cook on low-heat setting for about 1-1/2 hours or until heated through. Sprinkle with the remaining 2 tablespoons green onions. Serve dip with Crispy Pita Chips