Process onion and mushrooms through food processor until they resemble ground beef.
Heat large skillet over medium high heat. Add ground beef, onions, mushrooms, and taco seasoning. Break up meat and stir occasionally. Cook until moisture is gone and ground beef begins to brown, about 10-15 minutes.
Serve taco meat in hard or soft shells, in a burrito, on scrambled eggs, or on your taco salad.
Make your own homemade taco seasoning: https://selfproclaimedfoodie.com/homemade-taco-seasoning-recipe/