Preheat oven to 350 degrees F. In an extra-large skillet cook and stir mushrooms, sweet pepper, onion, and garlic in hot butter over medium heat until tender. Stir in flour, salt, thyme, and black pepper. Slowly stir in milk; cook and stir until thickened and bubbly. Stir in spinach, rice, Grilled & Ready® Diced Chicken, and 1/4 cup of the Parmesan cheese.

Spoon mixture into a 2-quart rectangular baking dish. Sprinkle with remaining Parmesan cheese. Bake, covered, 20 minutes. Uncover and bake about 10 minutes more or until heated through. Let stand 15 minutes before serving.