Preheat oven to 425 degrees F (220 degrees C). Grease a baking pan.
Combine pastry flour, baking powder, and 1/2 teaspoon salt in a bowl. Mix well. Cut in 1/4 cup margarine with a pastry cutter or 2 knives until mixture resembles coarse oatmeal. Mix in buttermilk, 2 tablespoons at a time, until a soft dough is formed and no dry spots remain. Roll dough out into a 1/2- to 3/4-inch layer; cut out into circles using a biscuit cutter or aluminum can. Place dough circles on the prepared pan.
Bake in the preheated oven until golden brown, 10 to 12 minutes.
Heat a large nonstick skillet over medium-high heat. Add olive oil and onion; saute until softened and translucent, about 5 minutes. Add garlic; saute until fragrant, about 1 minute. Add tofu; cook and stir until slightly browned, about 6 minutes. Toss in zucchini and green bell pepper; cook until tender, about 5 minutes. Season with salt and pepper.
Melt 3 tablespoons margarine in a saucepan over low heat. Add all-purpose flour; cook and stir until paste-like, about 2 minutes. Increase heat to medium; cook for 2 minutes. Whisk in stock slowly; bring to a boil. Cook until thickened to your desired consistency, about 5 minutes. Remove from heat.
Tear biscuits in half; scoop tofu mixture over biscuit pieces and pour gravy on top.