Preheat oven to 360 degrees F. I find this temperature perfect for many gourmet cookies.
In a large mixing bowl cream the butter, sugars, and salt. Mix on low speed for a minute, then on medium for an additional minute.
Add the eggs and vanilla extract. Mix on low speed until the eggs are blended in, then on medium for a minute and then on high for an additional minute. The mixture should be pale yellow and very fluffy.
Continuing on low speed, add the flour, along with the baking powder and baking soda, and mix until the flour disappears. Then add the oats and mix on low again, just until blended.
Add the chocolate chips, coconut, and walnuts, saving a little of each for the last bit of cookie dough. Mix on low just until blended.
Use a 2 ounce (medium-sized) cookie scooper and place the dough on ungreased non-stick baking sheets about 2" apart. Press the dough down lightly.
Bake in a preheated oven for 10-12 minutes, or until the tops start to crackle and are light golden brown.
For crispier oatmeal cookies: Decrease the rolled oats to 3 1/2 cups and press the dough down about halfway before baking.
Serve warm or cool completely before storing in an airtight container. These cookies also freeze well for up to 6 months.