In a large bowl, cream shortening, brown and white sugars, and eggs. Beat until well blended. Beat in vanilla extract and lemon juice. Stir in flour, baking soda and salt and mix well. Fold in macadamia nuts and oats. Cover and chill for 4 hours.
Preheat oven to 325 degrees F (165 degrees C). Lightly grease 2 baking sheets. Drop the dough by spoonfuls 2 inches apart on cookie sheets.