Preheat oven to 375°F. Melt butter in small skillet on medium heat. Add onion; cook and stir 3 minutes or until softened. Cool slightly. Mix seasonings in small bowl. Reserve 1 tablespoon seasoning mixture for vegetables.
Mix bread and milk in large bowl. Add ground beef, cooked onion, eggs and remaining seasoning mixture. Shape into a loaf on foil-lined 15x10x1-inch baking pan.
Toss vegetables with oil in large bowl. Add reserved seasoning mixture; toss again. Place vegetables around meat loaf.
Bake 55 to 60 minutes or until meat loaf is cooked through and vegetables are tender. Let stand 10 minutes before serving.