Preheat your oven to 350°F. While it heats, prepare all your ingredients: finely dice the onion into small, uniform pieces (about 1/2-inch), mince the garlic cloves, and measure out the rolled oats, Worcestershire sauce, ketchup, salt, and pepper. Having everything ready before you start mixing ensures the meat doesn't sit around too long, which can make it tough when cooked.

Crack the room-temperature eggs into a large mixing bowl and beat them lightly with a fork until the whites and yolks are fully combined. The eggs act as a binder that holds the meatloaf together, and room-temperature eggs incorporate more smoothly into the meat mixture without creating cold spots.

Add the ground beef, prepared onion, minced garlic, rolled oats, Worcestershire sauce, salt, and pepper to the bowl with the beaten eggs. Using your hands, gently mix everything together until just combined and the mixture becomes sticky—this should take about 1-2 minutes of mixing. I prefer to use my hands rather than a spoon because you have better control and can feel when the ingredients are evenly distributed without overworking the meat, which would make the final loaf dense and tough.

Transfer the meatloaf mixture to a standard baking dish and gently shape it into a loaf approximately 2 inches thick. Spread the ketchup evenly across the top of the loaf. The ketchup will caramelize slightly during baking, creating a flavorful crust that complements the savory meat.

Place the meatloaf in the preheated 350°F oven and bake for approximately 1 hour, or until the internal temperature reaches 160°F when measured with a meat thermometer inserted into the thickest part of the loaf. The oats absorb some of the meat's moisture during cooking, so checking the temperature ensures doneness without drying out the finished loaf.

Remove the meatloaf from the oven and let it rest in the baking dish for 5-10 minutes before slicing. This resting period allows the juices to redistribute throughout the loaf, ensuring each slice stays moist and flavorful rather than releasing all its juices onto the plate.