To Make Filling
In a food processor, pulse onion, celery and bell peppers until finely chopped. Set aside.
In a large dry skillet, toast bulgur over medium high heat, stirring often, until lightly browned, about 3 minutes. Transfer to a bowl, set aside.
Add beef to skillet and cook over medium heat, breaking up clumps with a fork, until browned, about 3 minutes. Transfer to paper towels and blot fat.
Dry skillet with paper towel; add oil and heat over medium heat. Add reserved vegetables and cook, stirring, until they start to brown, 8 to 10 minutes. Add flour and stir 1 minute. Add broth, barbecue sauce, Worcestershire sauce, and reserved beef and bulgur. Cook, stirring, until thickened, about 10 minutes. Season with salt and pepper and set aside. (The filling will keep, covered in the refrigerator for two days. Reheat before continuing.)
To Make Crust and Bake Pie
Preheat oven to 450 degrees F.
In a mixing bowl, whisk flour, baking powder, baking soda, salt, celery seed, and parsley. In a glass measuring cup, combine buttermilk and oil. Add wet ingredients and stir with a fork just until combined.
Turn dough onto a floured surface and knead gently 7 to 8 times. With floured rolling pin, roll into an 8 inch circle. Flour a fluted pastry wheel and cut dough into 6 triangles.
Spoon reserved filling into an ungreased 9 1/2 inch, deep-dish pie pan. Arrange biscuits evenly over filling. Bake for 20 to 30 minutes, or until bubbling. Let stand 5 minutes before serving.