Preheat the oven to 400°F. Lightly coat a large sheet pan with cooking spray.
Add potatoes to the sheet pan. Drizzle with 2 tbsp olive oil and season with garlic powder, 1/2 tsp salt, and 1/4 tsp pepper. Toss until evenly coated, then spread into an even layer. Bake for 10 minutes.
In a large bowl, lightly beat the egg with a fork. Grate the onion directly into the bowl, then add Italian seasoning, tomato paste, panko, Worcestershire sauce, milk, parsley, 3/4 tsp salt, and 1/2 tsp pepper. Whisk until combined. Add ground beef and gently mix just until combined. Avoid overmixing, which can make the meatloaf dense.
Divide and shape the mixture into 8 mini meatloaves (about 100 grams each). Remove potatoes from the oven and toss. Push potatoes to one side of the pan. Arrange meatloaves in the center section and spread ketchup evenly over the tops. Return the pan to the oven and bake for 15 minutes.
Remove the pan from the oven. If needed, blot excess grease with paper towels. Place green beans in the empty section of the pan. Drizzle with 1 tbsp olive oil and season with 1/4 tsp salt and a pinch of pepper. Toss to coat.
Return the pan to the oven and bake for 15–20 more minutes, or until potatoes and green beans are tender and meatloves reach an internal temperature of 160°F
Serve immediately.
Notes
Inspired by Cooking Light. Mini meatloaves adapted from Food Network.Storage: Store leftover meatloaf, roasted potatoes, and green beans in separate airtight containers in the fridge for 3–4 days.