In a medium omelet pan or non-stick skillet, add the olive oil and heat over medium heat. Add the mushrooms and cook until brown and tender, about 5-6 minutes. Remove the mushrooms from heat and transfer to a bowl.
Wipe the pan clean with a paper towel, and spray with a non-stick spray. Preheat the pan over medium heat.
In a small bowl, whisk together the eggs and a dash of salt and black pepper. Pour the eggs carefully into the preheated pan. Cook until the edges have begun to set and the bottom has browned, about 6-7 minutes. Run a small rubber spatula around the edges of the eggs so as to release it from the pan and then slide it onto a plate.
On half of the omelet, layer the sautéed mushrooms, spinach, goat's cheese and avocado. Fold the other half over the veggies and sprinkle with fresh parsley.