Heat oven to 350°F. Spray 9-inch round metal cake pan with cooking spray. For topping, combine oats, flour and brown sugar in small bowl. Cut in peanut butter and softened margarine with two knives or fingertips until mixture is crumbly; set aside. For cake, combine flour, oats, brown sugar, baking powder and salt in large bowl; mix well. In small bowl, combine milk, melted margarine, egg and vanilla; blend well. Add to dry ingredients all at once; stir just until dry ingredients are moistened. (Do not overmix.) Pour into pan. Spoon jelly by teaspoonfuls randomly over batter. Crumble reserved topping evenly over batter. Bake 35 to 40 minutes or until golden brown and wooden pick inserted in center comes out with just a few moist crumbs clinging to it. Cool 10 minutes in pan on wire rack. Cut into wedges; serve warm.