Peanuts, first processed by steaming, drying and then grinding, have been used in acontrol cookie as a fat substitute for both butter and margarine. Ground peanuts weresubstituted for 20% and 30% of butter and margarine in the cookie (by total weight offat). Physical properties and sensory evaluation indicated that the cookie partiallysubstituting ground peanuts for butter had no significant difference from the cookiethat partially substituted ground peanuts for margarine at the same level. The resultsshowed that the sensory acceptance of cookies using 20% ground peanuts as a fatsubstitute was lower than the control, with no change in cookie spread, lightnessvalue and TBA value. Effects of ground peanuts were found to decrease cookiespread, moisture content and high cutting force. The cookie that used 20% groundpeanuts as fat replacer had higher protein and lower fat content than the control. Thecookie had high moisture and low cutting force after being kept in a high densitypolyethylene bags at room temperature (28 oC). No bacteria were found after storingfor a 28-day period.