Preheat oven to 350 degrees F.
Sauté onions until translucent.
Add garlic and sauté a minute more. Remove to a bowl.
Add mushrooms to the hot pan and saute until mushrooms have given off their own liquid and it has begun to evaporate.
Combine mushrooms, onion, garlic, and walnuts in food processor. When smooth, add in oatmeal or ground rolled oats.
Season with onion and garlic powders and salt and pepper.
Add some olive oil to a pan, when hot form burger patties and place in hot pan. Cook for a few minutes on each side until brown.
Place browned burgers on prepared baking sheet and bake in oven for 10 - 15 minutes. Remove from oven and allow to cool.
Garnish with grilled onions, avocado, tomato, lettuce, and your favorite burger toppings!