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In the south-central region of the State of Chihuahua, the invasion of African grasses has changed the composition and dynamics of rangelands. The objectives of this study was to determine the botanical composition of the cattle diet and estimate a preference index in an invaded area with natal grass (Melinis repens) area. This research was conducted in the ranch ‘Salinas', located in the municipality of Satevó, state of Chihuahua, Mexico. Samples were taken from animals with an esophageal fistula. The collected samples were analyzed by the microhistological technique. The diet selected by the cattle consisted of 58% grasses and 42% forbs and shrubs (growth stage); however on later sampling dates, grasses represented up to 80% of the diet. During the four sampling dates of this study, cattle diet consisted mainly of natal grass on the following stages: growing 26.67%, 29.27% developing, and 28.86% and 35.53% at maturity and latency stages, respectively. Native species such as sideoats grama (Bouteloua curtipendula) and blue grama (Bouteloua gracilis), accounted from18 to 23% of the diet during all the sample dates. The highest preference index (12.63) was for the poverty threeawn (Aristida divaricate) and leather weed (Croton pottsii) with 12.95, during the growth stage. In contrast the lowest preference index was for natal grass with a range of 0.50 to 0.61. The botanical composition of the cattle diet consisted mainly of natal grass.