Heat the oven to 375°F and coat a 9-by-13-inch baking dish with cooking spray.
Stir the orzo, artichokes, spinach, broth, half-and-half, cream cheese, garlic powder, salt and black pepper together in the dish.
Cover tightly with foil and bake for 20 minutes.
Uncover carefully, stir from the bottom and reseal the foil before baking for 12 minutes more.
Test the orzo; if a piece has a firm white center, stir in 2 tablespoons hot water, cover and bake for 5 to 8 minutes more.
Stir until the cream cheese disappears into the sauce and rest for 5 minutes.