Although the breed contributes significantly to the genetic variation in the quality of beef, nutrition is one of the most important non-genetic factors. Nutrition significantly affects the rate of cattle growth, carcass composition and quality of meat and fats. Nutrition affects the change in the composition of beef fats (n-3/n-6 fatty acids ratio), and with consumption of fish oil and fish meal increases the proportion of n-3 fatty acids. It is possible to manipulate the proportion of fatty tissue and also the proportion of polyunsaturated fatty acids and saturated fatty acids in fatty tissue. Lately, manipulation receive gets great attention, first due to the anticancer properties of CLA, and second because fats of ruminants fed on pastures are rich in CLA content. Beef quality is manipulated by nutrition which affects its qualitative properties: marbling, tenderness, water binding capacity, taste, smell, pH, look and color. More recently, the effect of nutrigenomics on the quality of beef is being investigated. Nutrigenomics represents a strong relationship between the genetic base of the animal and the nutrient as the most important environmental factor. Technology, such as nutrigenomics, which accurately analyzes the influence of nutritional components on the expression of genes, can be essential for improving the quality of beef. Manipulation of beef quality through feeding will only remain viable as long as it is practical, economical and does not detract from the intrinsic and extrinsic attributes of beef quality, or any other aspect relating to environmentally acceptable or ethical beef production.