Preheat oven to 350°F.
Heat oil and onions in medium skillet on medium heat; cook 2-3 min. or until onions begin to soften. Add mushrooms; cook 5-7 min. or until liquid is evaporated and onions begin to brown. Add garlic; cook 30 seconds or until fragrant, stirring constantly. Remove from heat; cool slightly.
Stir 1 cup sauce and salt into skillet with onions. Combine sauce mixture, meats, egg, bread crumbs, Parmesan and parsley in large bowl.
Shape mixture into 9x5 inch loaf; place on rimmed baking sheet lined with foil. Bake 1 hour 15 min. or until done (165°F), topping with additional 1/2 cup sauce and shredded cheese during the last 15 min. of baking. Let stand 5-10 min. before slicing and serving with remaining sauce.