Heat oven to 350°F. Grease bottom and sides of 13x9-inch pan with shortening. In large bowl, beat butter and brown sugar with electric mixer on medium speed until well mixed. Beat in 1 cup flour, the oats, cinnamon, baking soda and pecans until well blended and crumbly. Press half of the crumbly mixture in bottom of pan to form crust. Reserve remaining crumbly mixture for topping.