Ensure that the mushrooms are not cold. If they’re coming from the refrigerator, place them in a large bowl and microwave them 30 seconds at a time tossing between. Heat until they not cold but just slightly warm.
Melt butter in a small sauce pan.
Add Worcestershire, salt, garlic powder and onion powder. Stir to combine.
Pour sauce over top of mushrooms in a large bowl. Toss until they’re all evenly coated.
Let sit for 20-30 minutes, tossing on occasion to keep the mushrooms coated. If the butter starts to set up and look chunky, microwave for 20 seconds and stir until the sauce is no longer clumping.
Grill mushrooms until nicely browned on all sides.
