Heat oil in a large skillet over medium heat. Add garlic, and cook, stirring until fragrant, about 1 minute. Add escarole hearts, and cook for 1 minute. Add remaining leaves, and cook, stirring until bright green and wilted, about 2 minutes more. If necessary, add a few tablespoons of water to aid in wilting. Add butter, and stir until melted. Season with salt and pepper. Serve with lemon wedges on the side.