In A Large Saucepan, Saute Onion In Butter Until Tender. Stir In The Tuna, Soup, Milk, Garlic Salt, Oregano And Pepper Until Combined. Spread 3/4 Cupful Into A Greased 11-In. X 7-In. X 2-In. Baking Dish. Layer With Three Noodles (Trimming If Necessary), 3/4 Cup Tuna Mixture, Half Of The Cottage Cheese And A Third Of The Mozzarella Cheese. Repeat Layers. Top With Remaining Noodles, Tuna Mixture And Mozzarella. Sprinkle With Parmesan Cheese. Bake, Uncovered, At 350 Degrees F For 25-30 Minutes Or Until Bubbly. Let Stand For 10-15 Minutes Before Serving.