Preheat oven to 350 degrees F. Line 13x9x2-inch baking pan with foil; set aside. In mixing bowl beat 1/2 cup of the butter on medium to high 30 seconds. Add 1 cup of the brown sugar, the baking soda, and salt. Beat until combined, occasionally scraping bowl. Beat in 1 egg and 1/2 teaspoon of the vanilla. Beat or stir in 1-1/4 cups of the flour. Stir in oats; set aside.
For filling, in saucepan stir remaining 1-1/2 cups brown sugar and 1/2 cup butter over medium heat until combined; cool slightly. Stir in remaining 3 eggs and 1 teaspoon vanilla; lightly beat with wooden spoon. Stir in remaining 1-1/4 cups flour and the chocolate.
Set aside 3/4 cup oats mixture; press remaining in pan. Spread filling, top with cherries, dot with reserved oats mixture, and sprinkle nuts. Bake 25 minutes, until top is light brown and filling is moist. Cool on rack 1 hour. Cover and refrigerate at least 2 hours.
Lift from pan; cut with serrated knife. Store, covered, at room temperature. Makes 25 bars.