The primary ingredient in muesli is rolled oats. Muesli is a cold cereal typically made from a mix of rolled oats, nuts, seeds, and dried fruits. It originated from Switzerland in the late 19th century and is commonly served with milk or yogurt. The oats provide essential carbohydrates, fiber, and protein, making muesli a popular choice for a nutritious breakfast. Variations of muesli may include additional ingredients like fresh fruits, honey, or spices. Overall, the simplicity and versatility of muesli contribute to its appeal as a healthy meal option.