This is the best basic meatloaf recipe and a terrific choice for a simple family dinner.
Preheat oven to 350 degrees. Line a baking sheet with parchment paper.
In large bowl mix together the ground sirloin, oats, milk, onion, egg, salt and pepper until well combined. Shape into a loaf on the parchment paper lined baking sheet.
In a smaller bowl, whisk together the ketchup, brown sugar and mustard. Spread evenly over the top and sides of the meatloaf.
Bake the meatloaf for 60 minutes, or until a meat thermometer registers the center of the meatloaf is cooked to 160 degrees F.
Remove meatloaf from oven and allow to rest for five minutes before serving.