Heat the oven to 400° with a rack in the center position.
Toss the potatoes on a rimmed baking sheet with 1 tbsp. of the olive oil and a sprinkle of salt. Spread them evenly, then set a wire rack on top.
In a large bowl, gently combine the beef, garlic powder, onion, bread crumbs, and 3/4 cup barbecue sauce. Shape the mixture into 4 small loaves and place them on the wire rack over the potatoes.
Bake the potatoes and meat loaves for 30 minutes. Meanwhile, toss the green beans with the remaining olive oil and a pinch of salt.
Remove the pan from the oven. Brush the loaves with the remaining barbecue sauce and scatter the green beans around them. Return the pan to the oven and bake until the potatoes and beans are tender and a thermometer inserted into a meat loaf registers 150°, about 12 minutes more.