A method for producing quick-cooking or instant parboiled cereals comprising: - a step of soaking or hydrating grains wherein the grains are immersed in water at a temperature less than the gelatinisation temperature (Tg) of the cereal being processed, the soaking step being regulated in such a way that the moisture content reached by the grains is between 27% and 32%, - a step of cooking hydrated grains performed by subjecting the grains to a temperature greater than the gelatinisation temperature (Tg) of the cereal being processed, in a moist environment, wherein the cooking step is performed in an autoclave using saturated steam introduced at a pressure of between 10 kPa (0.1 bar) and 150 kPa (1.5 bar), preferably 10 kPa (0.1 bar) and 80kPa (0.8 bar), - a microwave heating step performed immediately after the cooking step, - a step of controlled drying and tempering in such a way as to bring the grains to an average value of humidity equal to 16% - 18% with a moisture content differentiated between the outer and surface part of the grain and the core of the grain, the moisture content of the outer and surface part of the grain being between 8% and 10%, wherein the drying and tempering step comprises a sequence of at least two, preferably four intermediate steps each operating at a predetermined drying temperature greater than the drying temperature of the intermediate step which immediately follows and wherein the drying and tempering step takes place in a rotary dryer with compartments, preferably supplied with air, with separate sections defining, respectively, the intermediate steps, - a step of rolling the grains wherein the grains are uniformly compressed, the rolling step being regulated in such a way as to obtain transversal cracking of the outer and surface part of the grain and wherein during the rolling step the grains are compressed uniformly using smooth rollers rotating at equal speeds and in opposite directions. - a step of soaking or hydrating grains wherein the grains are immersed in water at a temperature less than the gelatinisation temperature (Tg) of the cereal being processed, the soaking step being regulated in such a way that the moisture content reached by the grains is between 27% and 32%, - a step of cooking hydrated grains performed by subjecting the grains to a temperature greater than the gelatinisation temperature (Tg) of the cereal being processed, in a moist environment, wherein the cooking step is performed in an autoclave using saturated steam introduced at a pressure of between 10 kPa (0.1 bar) and 150 kPa (1.5 bar), preferably 10 kPa (0.1 bar) and 80kPa (0.8 bar), - a microwave heating step performed immediately after the cooking step, - a step of controlled drying and tempering in such a way as to bring the grains to an average value of humidity equal to 16% - 18% with a moisture content differentiated between the outer and surface part of the grain and the core of the grain, the moisture content of the outer and surface part of the grain being between 8% and 10%, wherein the drying and tempering step comprises a sequence of at least two, preferably four intermediate steps each operating at a predetermined drying temperature greater than the drying temperature of the intermediate step which immediately follows and wherein the drying and tempering step takes place in a rotary dryer with compartments, preferably supplied with air, with separate sections defining, respectively, the intermediate steps, - a step of rolling the grains wherein the grains are uniformly compressed, the rolling step being regulated in such a way as to obtain transversal cracking of the outer and surface part of the grain and wherein during the rolling step the grains are compressed uniformly using smooth rollers rotating at equal speeds and in opposite directions.