Preheat oven to 350 degrees F (175 degrees C). Grease the sides and bottom of one 15×10 inch pan.
In a large bowl combine the flour, 1/2 cup sugar, margarine or butter and salt until the mixture resemble coarse crumbs. Press firmly into the prepared pan.
Bake at 350 degrees F (175 degrees C) for 20 minutes.
In a large bowl stir the eggs, corn syrup 1 1/2 cups white sugar, melted margarine and vanilla until blended. Stir in the chopped pecans.
Spread the filling evenly over the hot crust. Bake at 350 degrees F (175 degrees C) for 25 minutes or until set. Let cool before slicing.