Preheat oven to 350°F. Lightly spray the bottom of a 9x13-inch baking dish with cooking spray.
In a large bowl, whisk together the egg and milk.
1 large egg, ¾ cup milk
Stir in the shredded cheddar cheese, quick-cooking oats, chopped onion, and salt.
1 cup shredded cheddar cheese, ½ cup quick-cooking oats, ½ cup chopped onion, ½ teaspoon salt
Crumble the ground beef over the mixture and gently mix until combined.
1 pound ground beef
Shape the mixture into eight equal mini loaves and place them in the prepared baking dish.
In a small bowl, combine the ketchup, brown sugar, and prepared mustard. Spoon the glaze over the meatloaves.
⅔ cup ketchup, ½ cup packed brown sugar, 1½ teaspoons prepared mustard
Bake uncovered for 25-30 minutes, until a thermometer inserted near the center reads 160°F.
Notes
🥡 Storage: Refrigerate leftovers in an airtight container for 3-4 days.♨️ Reheating: Reheat covered in a 325°F oven or in the microwave until the center reaches 165°F.❄️ Freezing: Freeze cooled meatloaves in an airtight container for up to 3 months. Thaw overnight in the refrigerator.💡 Tips: Mix gently, form evenly sized loaves, and use a thermometer to check doneness.🍳 Alternate Methods:Slow cooker: Arrange the mini loaves in a lightly greased slow cooker in a single layer, preferably on a small foil rack or parchment sling to keep them above excess juices. Spoon the glaze over the tops. Cook covered on LOW for approximately 3-4 hours or HIGH for 2-3 hours, checking early, until the centers reach 160°F. The glaze will be softer than when baked.Air fryer: Cook in batches at 350°F, checking after about 15 minutes, until the centers reach 160°F.♻️ Leftovers: Slice into sandwiches, crumble into pasta sauce, or add to a breakfast hash.📝 Notes: Ground turkey or chicken can be used instead, but cook poultry to 165°F. Cooking times vary with loaf size and appliance.