In 3-quart saucepan, melt margarine.
Remove from heat. Add sugar, flour, cocoa, baking soda, salt, eggs and vanilla extract. Stir with spoon until batter is well blended and smooth.
Stir in 1 1/2 cups chocolate chips.
Spread into 9x13-inch pan.
Sprinkle with remaining chips.
Bake for 25-30 minutes.