Heat oven to 350 F. Grease 13x9-inch pan. Reserve 2/3 cup of the dry cake mix for filling. In large bowl, combine remaining dry cake mix, margarine and 1 egg at low speed until well blended. Press in bottom of greased pan. Bake at 350 F. for 15 to 20 minutes or until light golden brown.

In large bowl, combine reserved 2/3 cup dry cake mix, brown sugar, corn syrup, vanilla and 3 eggs at low speed until moistened. Beat 1 minute at medium speed or until well blended. Pour filling mixture over warm base; sprinkle with pecans. Bake an additional 30 to 35 minutes or until filling is set. Cool completely. Cut into bars. Store in refrigerator. 36 bars.