Preheat oven to 375°F. Lightly grease a 13 x 9 x 2-inch baking pan; set aside. Cream butter and sugars until light and fluffy; beat in vanilla and eggs. Stir in 2 1/4 cups flour mixed with baking powder and salt; blend well. Divide batter in half. Blend together cocoa powder and melted butter; stir into one half the dough; spread evenly into prepared baking pan. To the remaining dough, stir in 1/4 cup flour and 1/2 cup "M&M's"(r) Semi-Sweet Chocolate Mini Baking Bits; spread evenly over cocoa dough in pan. Sprinkle with remaining 1/2 cup baking bits. Bake 25 to 30 minutes or until edges start to pull away from sides of pan. Cool completely. Cut into bars. Store in tightly covered container.