Position rack in center of oven and preheat oven to 350°F.
In a large bowl, combine the oats, coconut, pecans, and walnuts. In a measuring cup or small bowl, whisk together the melted coconut oil, pumpkin puree, pumpkin pie spice, and salt. Drizzle the oil/pumpkin mixture over the dry ingredients in the bowl and stir well to combine. Drizzle the maple syrup on top and mix until all ingredients are evenly coated.
Transfer the granola onto a 13"x18"x1" rimmed half sheet pan and spread into an even layer. Bake, stirring and flipping with a wooden spoon every 10 minutes, until the mixture turns a nice, even, golden brown, about 30 minutes total. Watch carefully for the last 10 minutes of baking time, checking every few minutes and stirring as necessary to prevent over-browning.
Remove the granola from the oven and stir frequently as it cools, scraping the bottom of the pan to prevent sticking. Once completely cool, store in an airtight container.
TO MAKE A DOUBLE BATCH, double all of the ingredients and then divide the unbaked granola between two rimmed sheet pans. Move the oven racks to just above and just below the center rack position. And then every ten minutes, when taking out the granola to stir it, switch (from bottom to top and top to bottom) and rotate the pans when putting them back in the oven. Baking a double batch often takes closer to 40 minutes than a single batch's 30 minutes...so as always, watch closely the first time you make it.
Similarly, if you decide TO CUT THE RECIPE IN HALF, be prepared for it to take less total time to bake.
Make sure your nuts are raw since they will get toasted as the granola bakes.
You may substitute melted butter or a mild-flavored extra-virgin olive oil in place of the coconut oil.
You may substitute honey or agave for the maple syrup, but keep in mind that these alternatives will give the granola a slightly different taste.
You may substitute pumpkin seeds (pepitas) for some or all of the chopped nuts.
Since homemade granola tends to stick to the pan if not stirred very frequently during the cooling process, I've found that using a Silpat or some parchment paper on the bottom of your sheet pan alleviates this problem. You just have to stir carefully to make sure the granola doesn't wind up stuck under the parchment paper.