Grease bottom and side of 15 x 10 baking pan.  Combine flour, sugar, margarine and salt until it resembles coarse crumbs.  Press firmly and evenly into pan.

Bake at 350 for 20 min. 

Filling:  (prepare while crust is baking)

4 eggs, slightly beaten

1 1/2 cups light Karo syrup

1 1/2 cups sugar

3 Tablespoons margarine, melted

1 1/2 tsp. vanilla

2 1/2 cups chopped pecans

Combine eggs, syrup, sugar, margarine and vanilla until blended.  Stir in pecans.  Spread evenly over hot crust.  Bake at 350 for 30 minutes or until set.  Cool before cutting into bars.