preheat oven to 375

cook noodles

in a medium skillet add oil and saute onions and mushrooms over medium-low heat until mushrooms begin to release moisture, about 10 min.

in a large mixing bowl combine sauteed onions and mushrooms and all remaining ingredients, reserving 1 cup cheddar cheese for the to

add the tuna mixture to a 3 quart casserole dish or 9" baking pan, top with 1/2 cup of remaining cheddar cheese.

bake 15 min covered and 10 min uncovered or until cheese is hot and bubbly.