Preheat oven to 375°F. Grease a 9×9 (or 10×10) baking dish. A 9×13 also works.
Brown the ground beef in a skillet with garlic powder, onion powder, black pepper, and salt. Cook just until no longer pink. Drain the grease from the ground beef.
Spread the cooked beef evenly across the bottom of the baking dish.
Pour the uncooked rice evenly over top — do NOT stir.
Pour in the 2 cans of beef consomme.
Spoon the French onion soup over the top, lightly spreading so it covers the surface. (Use ALL of the liquid and everything from the can)
Scatter the sliced mushrooms over everything.
Drizzle the melted stick of butter evenly over the top.
Sprinkle the Locatelli Pecorino Romano over everything.
Cover tightly with foil and bake 60 minutes.
Remove foil, gently fluff with a fork, then return to oven uncovered at 375°F for 15 minutes to remove excess liquid and brown the top.
Let rest 5 minutes before serving — rice continues to steam and finish.