Disclosed are improved methods for preparing a grain based extrudate involving high screw speeds, short barrel length extruders and short residence times. Preferred methods of preparation reside in methods for preparing the present improved RTE cereal or snack products. The preferred methods contain the steps in sequence of feeding an at least partially ungelatinized grain based material to a cooker extruder having at least one rotating screw, said cooker extruder including a barrel preferably having a relatively short length to diameter ("L/D") ratio of substantially less than 12; working the grain based material by rotating the screw at a rotational speed of at least 700 rpm to mix and heat the cereal material and to compress the grain based material; and extruding the plasticized mass through at least one die orifice to form an extrudate. Its preferred product aspect provides RTE cereal or snack products in the form of a puffed grain based product piece having a density of about 10 to 100 g/l., a moisture content of 1.5% to 5%, and cell sizes expressed in cross sectional areas at the maximum diameter ranging from about 0.001 to 3 square millimeters with the majority of the cell sizes being substantially less than 1.0 square millimeters.