Heat oven to 350ºF.
In a medium skillet, heat oil over medium heat. Add mushrooms; cook 4 to 5 minutes or until tender, stirring occasionally.
In a large bowl, whisk eggs until blended. Stir in 1-1/2 cups of the cheddar cheese, cottage cheese, Hot Links and green onion.
Pour into greased 9"x13" baking dish.
Bake 40 minutes; sprinkle with remaining cheese. Bake 2 to 5 additional minutes, or until cheese is melted and top is light golden brown.