Step 1: Preheat oven to 400°F (200°C). Pierce each potato several times with a fork. Bake directly on the oven rack for 40-50 minutes, or until fork-tender.
Step 2: While potatoes bake, heat olive oil in a large skillet over medium-high heat. Add ground beef and chopped onion. Cook, breaking up the beef, until browned and the onion is softened, about 6-8 minutes. Drain any excess fat.
Step 3: Stir in minced garlic and cook for 1 minute more until fragrant. Add the taco seasoning and water. Bring to a simmer, then reduce heat and cook for 5-7 minutes, stirring occasionally, until the sauce has thickened.
Step 4: Once potatoes are cooked, carefully slice each potato lengthwise down the middle, being careful not to cut all the way through. Fluff the inside of the potato with a fork.
Step 5: Divide the seasoned ground beef mixture evenly among the four potatoes, stuffing it into the opened potatoes.
Step 6: Top each potato generously with shredded cheese. Return the potatoes to the oven for 5-10 minutes, or until the cheese is melted and bubbly.
Step 7: Remove from oven. Serve hot with your favorite taco toppings like sour cream, salsa, diced tomatoes, green onions, and avocado.