Orange Muffins With Crumb Topping

1. Preheat oven to 400ºF. Grease muffin cups or line with muffin liners.
2. For the muffins, combine flour, sugar, salt and baking powder. Place vegetable oil into a 1-cup measuring cup; add the egg and enough milk to fill the cup. Mix this with the flour mixture.
3. Clean the orange thoroughly and zest the entire orange into the batter. Squeeze a desirable amount of juice from the orange into the batter. Fill muffin cups right to the top, and sprinkle with crumb topping mixture.
3. To make the crumb topping, mix together brown sugar, flour, and butter. Mix with a fork till crumbly, and sprinkle over muffins before baking.
4. Bake for 20 to 25 minutes in the preheated oven, or until golden brown.