Heat oven to 375°F. Cook turkey and onion in oil in large skillet 8 to 10 minutes, breaking up meat, to 165°F.
Stir chili powder, cumin, filling salt, and garlic powder 30 seconds. Add beans, sauce, chiles, and broth; simmer 5 minutes.
Meanwhile, boil orzo with tablespoon salt to 3 minutes short of package time. Drain thoroughly; fold into turkey with 2 oz cheddar.
Transfer to deep 9-by-13-inch dish; add remaining cheddar. Foil-cover; bake 20 minutes.
Uncover; bake 8 to 10 minutes until bubbling and center 165°F. Rest 10 minutes before spooning into bowls.