In a large skillet, heat oil over medium-high heat. Add onions; cook and stir until tender, 2-3 minutes. Add garlic and oregano; cook and stir 1 minute longer. Stir in wine. Bring to a boil; cook until liquid is reduced by half, 3-4 minutes. , Transfer to a 5- or 6-qt. slow cooker. Add potatoes, beans, mushrooms, leeks and carrots. Stir in water, tomatoes, thyme, salt and pepper. Cook, covered, on low 8-10 hours or until potatoes are tender. Top with basil.