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The probability of soil water being available is about equal in summer and winter on the Northern Tablelands while on the western part of the Northern Slopes the winter probability is somewhat higher (1). On the other hand, winter temperatures in both regions limit plant growth so that summer pasture production is considerably higher than winter, even with frost tolerant grasses and legumes (1;2). In addition Aristida ramosa R.Br. is a widespread dominant grass on the Northern Slopes and parts of the Northern Tablelands and estimates of the cost of fleece contamination by its seeds range from $1.88 per sheep averaged over the years 1982 -1984 from 220 properties in the Tamworth -Manilla -Barraba district to $3.60 per sheep from one property near Barraba in 1988/89 (3). In addition, properties with heavy infestations can only carry around 3.5 DSE per ha compared with about 6 per ha on equivalent country that does not have wiregrass. Dramatic reductions in the abundance of A. ramosa and increases in the more valuable Danthonia linkii Kunth have been produced in small scale experiments with heavy summer grazing (4). The next step was to apply this approach to commercial paddocks and to examine the effects of heavy summer grazing on natural pastures on the Northern Tablelands.