Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine the ground beef, oats, salt, pepper, chopped onions, beaten egg, and half a can of cream of mushroom soup. Pour in the milk and sprinkle in the dried sage. Mix gently until everything is evenly incorporated.

Transfer the meat mixture into a greased 9 x 5 loaf pan, pressing it firmly to pack the ingredients together.

Place the loaf pan in your preheated oven and bake for 1 hour.

After baking, remove the meatloaf from the oven and let it rest for 10 minutes.

In a saucepan over medium heat, warm the remaining 1.5 cans of cream of mushroom soup. Gradually add milk while stirring until you reach your desired gravy consistency.

After the meatloaf has rested, drain any excess liquid and pour it into the gravy mixture. Stir well to incorporate the flavors.

Slice the Cream of Mushroom Meatloaf and serve it warm, topped with the creamy gravy.