Preheat the oven to 450°F. Lightly grease a 15 x 10-inch pan.
Combine the oats, sugar, butter, corn syrup, vanilla and salt and mix well. Press the mixture into the pan, using your lightly greased hands to help the process along.
Bake the squares for 12 to 15 minutes, or until they're a light golden brown. Remove them from the oven and cool completely on a wire rack.
In a medium saucepan set over very low heat, melt the chocolate and shortening together, stirring constantly until smooth. Spread the mixture evenly over the oat base and sprinkle on the chopped nuts. Cover very loosely and chill the squares in the refrig