1. Heat oven to 375 degrees F.
2. Heat oil in large nonstick skillet over medium-high heat. Add onions and cook 5 minutes, until lightly browned; cool. Combine onions, meats, the 2/3 cup sauce, the bread crumbs, egg, parsley, garlic, salt, and pepper in large bowl, tossing meatloaf mixture lightly with fingertips.
3. Divide mixture between six ungreased 4-inch (1-cup) individual fluted cake mold pans or one 8-1/2x4-1/2-inch loaf pan. Arrange pans on large jelly-roll pan. Bake 30 minutes (loaf pan: 60 to 70 minutes), until meat thermometer inserted into center of meat-loaves reaches 160 degrees F. Remove pans from oven and immediately unmold onto jelly-roll pan. Serve with marinara sauce, if desired, and garnish with chopped parsley, if desired. Makes 6 servings.