Heat the oven to 425ºF and grease a 9x13-inch baking dish.
Chop garlic cloves and combine with lemon juice, olive oil, yellow mustard, dried oregano, salt, and several grinds of black pepper in a large bowl.
Cut potatoes into wedges, add to the bowl, and toss to combine. Pour into a baking dish, pour some water, and cover tightly with foil.
Bake until the potatoes are fork tender, then uncover and bake until liquid is evaporated.