Preheat the oven to 375°F (190°C).
Peel and thinly slice the potatoes, dice the onion, and mince the garlic.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and minced garlic, sauté for 3-4 minutes until soft. Add the ground beef and brown for 6-8 minutes, draining excess fat.
Layer half of the sliced potatoes in a greased 9x13-inch baking dish, followed by half of the beef mixture and half of the mixed vegetables. Repeat the layers.
Cover with aluminum foil and bake for 45 minutes. Remove foil, sprinkle cheese on top, and bake uncovered for an additional 15-20 minutes until cheese is bubbly and golden brown.
Let the casserole cool for 5-10 minutes before serving.