Antibiotics are used in farm animals for therapeutic and prophylactic purposes; therefore meat and milk derived from animals   may contain trace quantities of these antibiotics or their metabolites which may cause adverse health effects on consumers. The current study was carried out to detect the residues of oxytetracycline and doxycycline in fat, muscle, liver and kidney of beef slaughtered in Beni-Suef Governorate, and also to study the effect of cooking (roasting and boiling) on these residues. A total of 80 cattle samples were collected from different butcher's shop in Beni-suef Governorate, (20 each of fat, muscle, liver and kidney samples), using LC-Mass-Mass/High Performance Liquid Chromatography (HPLC). The mean values of oxytetracycline residues in raw samples were 25.35±14.93, 12.2±6.72, 39.1±22.05 and 120.5±51.16 µg/kg b.w for oxytetracycline, while the mean values of doxycycline were 91.15±50.19, 12.04±6.61, 86.5±53.44 and 422.38±301.18 µg/kg b.w for fat, muscle, liver and kidney respectively. After heat treatment by boiling and roasting reduction was occurred in concentrations of oxytetracycline and doxycycline, in which boiling reduced the levels of oxytetracycline by 50% and 80%, while the percentage of reduction in roasting was 35% and 65% for muscle and kidney, respectively. On other hand Doxycycline was not detected after boiling and roasting of the samples with a reduction level of 100%.