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.
Spread apples over crust in pan. In 1-quart saucepan, heat 3/4 cup caramel topping and 1/4 cup flour to boiling, stirring constantly. Boil about 1 minute, stirring constantly, until slightly thickened. Drizzle over apples. Sprinkle with reserved crumbly mixture.
Bake 35 to 45 minutes or until top is golden brown. Cool 30 minutes before serving. Top with ice cream and additional caramel topping.