Preheat the oven to 400 degrees and line a large sheet pan with parchment paper.
In a mixing bowl, combine the ground lamb, breadcrumbs, egg, 2 minced garlic cloves, oregano, feta, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Mix until just combined, then shape into 4 small loaves and place them on one side of the sheet pan.
In the same bowl, toss the potato cubes with olive oil, remaining 2 minced garlic cloves, lemon zest, lemon juice, thyme, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until evenly coated.
Spread the potatoes on the other side of the sheet pan. Bake for 25 minutes.
Remove the pan from the oven, scatter the olives around the meatloaves and potatoes, and return to the oven for 10 more minutes until the meatloaves reach 160 degrees internally and the potatoes are golden.