Preheat oven to 375 degrees F (190 degrees C). In a large skillet, cook the beef, onion and celery over medium heat until beef is evenly browned. Drain off fat.
In a medium saucepan, melt butter over medium heat. Stir in flour, salt, pepper and garlic powder. Gradually stir in the beef broth until mixture boils and thickens. Add the cooked beef mixture and vegetables to the saucepan.
Place pie crust in a 9 inch pie pan. Pour the beef mixture into the crust. Cover with top crust, seal edges, and cut away excess dough. Make several small slits in the top to allow steam to escape.
Bake at 375 degrees F (190 degrees C) for 35 minutes or until crust is golden brown.