Place oatmeal in bowl with boiling water. Let stand for 10 minutes. In a mixer, mix margarine, brown sugar, white sugar, and eggs. Beat until smooth. Add the oatmeal slowly. Add flour, baking soda, vanilla, cinnamon and salt. Beat until smooth. Use a 9 x 13 x 2 long cake pan, greased and floured. Bake at 350 degrees for 30-35 minutes. Test for doneness with a toothpick.
While cake is baking make frosting--frosting must be spread on cake as soon as you take cake out of the oven
Use 1 cup brown sugar (packed), 1 cup Baker's coconut, 1/2 cup milk, and 1/2 cup chopped pecans.
Put brown sugar and milk in a saucepan. Bring to a boil. Add coconut and nuts. Stir. Pour over warm cake and place cake based on type of oven: for gas stoves with a broiler on the bottom, set oven to broil which is between 500-550 degrees. For electric oven, place cake on top rack and set to broil which is about 500 degrees (on most electric ovens, you have to let the door slightly ajar). For either type of stove, let cake bake another five minutes. Let cool before serving.