The first step is to place a very large pot of salted water over high-heat and preheat your Traeger to 225F.
Make the cheese sauce while you wait for the water to boil and cook the pasta. Set a medium sauce pot over medium heat. Add the heavy cream and room temperature cream cheese.
Whisk the cream mixture until it's smooth. Add two cups of the shredded cheddar, gouda, and monterey jack cheese.
Season with salt, pepper, onion powder, and dried mustard and stir well.
Cook the pasta but reduce cook time by 3 minutes.
Drain the cooked macaroni noodles and combine with the cheese mixture. Fold in half of the shredded cheese. Transfer the macaroni and cheese to a large skillet and top will the remaining one cup of shredded cheese.
Place directly on the grill grates of your hot Traeger and cook with the lid closed for 20-30 minutes.
Serve immediately and enjoy.