Technical Abstract: A case study was conducted to collect information on the use of a total mixed ration (TMR) on thirteen pasture-based dairy farms in New York and Pennsylvania with the objectives of monitoring TMR ingredient and nutrient content and summarizing what and how decisions are being made in relation to TMR formulation throughout the grazing season. In general, pasture replaced haylage/silage in the TMR diet on a 1:1 basis, and protein level was often decreased in the TMR due to high pasture protein levels. Very few farms forage tested their pastures, even though forage testing of stored forages was common. Amount of TMR fed was frequently adjusted on most farms based on bulk tank readings, changing pasture availability, and TMR refusal rates. Flexibility is key in utilizing a TMR on pasture-based operations to respond to changing pasture quality and quantity and to formulate least-cost rations. The basic principles of nutrition still apply- monitor dry matter intake, forage to concentrate ratios, and milk production. This fact sheet summarizes this research project at the USDA-ARS Pasture Systems and Watershed Management Research Unit in University Park, PA.