Marsanne is primarily used to add particular characteristics to blends. The grape is often picked before it is fully ripe and then blended with more flavorful grapes to add acidity. This is the case in the Languedoc region of Southern France where it is blended with Viognier. Marsanne is rarely aged in new oak and makes wines that are very light yellow and can have a slight greenish tint.
The Marsanne grape has not really hit its stride in California, though a few good examples are made. Tablas Creek Winery is located in the warm Paso Robles wine region and specializes in Rhone varietals. They make an excellent white blend that includes a substantial amount of Marsanne. Tablas Creek keeps yields in check and is able to grow grapes with distinctive minerality and acidity.
The grape is originally from the town of Marsanne in the Northern Rhone Valley of France. It makes up the majority of the white blends in Hermitage, Crozes-Hermitage and St-Joseph. Marsanne is blended with the more complex, but less reliable Roussanne to make these wines. Marsanne is more widely planted in the Rhone Valley than Roussanne. It has simpler flavors, but is a more reliable varietal to grow.