Buy a "fajita pack" from the store. It's in the produce aisle. It's onions, green peppers, and onions. If you want to buy them separately that's fine. It just takes more time. Take the veggies and put them in your dehydrator. Cover them with plastic to keep them soft.
For the mushrooms, slice them, marinate in salt and olive oil (or Bragg's Liquid Aminos and olive oil). I don't measure these. I do it by sight. Add minced garlic. Dehydrate veggies and mushrooms for about 2 hours.
Put the veggies on top. Add avocados and cilantro. To bring out the flavor, squeeze lime juice over everything. (The lime is VERY important. Don't add more salt until you've added the lime juice and tasted your fajita. If you want more salt, add it then.)
Me and Raymond LOVE these things. Easy pacheesy!