Heat up the grill--med-high. Wipe clean or wash mushrooms under running water, be sure to towel dry them. Put cleaned mushrooms in a bowl.
Drizzle olive oil over mushrooms to coat all mushrooms. Sprinkle course garlic salt with parsley over mushrooms. Sprinkle parmesan cheese. Sprinkle basil and some parsley flakes. Crack some fresh black pepper. Mix them thoroughly to coat the oil all over mushrooms and the seasonings dispersed. This is about personal preference with seasonings, start out mild and add if you like more.
Put all the mushrooms directly on the preheated grill, feel free to turn the bowl over and drizzle the oil from the bottom of the bowl right over the mushrooms on the grill. Let them cook for 5 minutes, move them around on the grill a bit and let them heat for another 2 minutes. Remove from grill and serve whole with anything!