In a large pot of salted boiling water cook the eggs noodles according to package instructions until al dente. Drain, drizzle with a little olive oil and set aside.
In a medium-sized bowl, combine all topping ingredients and set aside.
In a medium-sized skillet, melt ½ tbsp of butter over medium-high heat and saute the onions, celery, and bell pepper until tender. Season with salt and pepper.
Place the sauteed veggies, tuna, peas, oregano, condensed cream of mushroom soup, milk, one cup shredded cheddar cheese, one tablespoon parsley, and cooked noodles in a large bowl and mix with a rubber spatula until well combined.
Spoon the mixture into a casserole dish and sprinkle the topping evenly over the mixture. Bake for 20 minutes or until golden brown.