1Heat oven to 350°F (325°F for dark or nonstick pan). Grease bottom only of 13x9-inch pan with shortening or cooking spray.
2Mix oats, flour, brown sugar and baking soda in medium bowl; stir in butter. Reserve 1 cup of the oat mixture. Press remaining oat mixture in pan. Bake 10 minutes; cool 5 minutes.
3Stir brownie mix, pouch of chocolate syrup, water, oil and eggs in medium bowl, using spoon, until well blended. Stir in nuts. Carefully spread over baked layer; sprinkle with reserved oat mixture.
4Bake 40 to 45 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool completely, about 2 hours. For brownies, cut into 8 rows by 5 rows. Store tightly covered.