In this chapter, the crop characteristics that have already been modified through plant breeding are discussed in addition to the concept of a productive oat ideotype based on in-depth knowledge of underlying physiological processes. During the past 10 years in particular, numerous studies reporting genetic gains in the grain yield production of cereals have been published. Regarding genetic gains in oat productivity, Lawes, Wych and Stuthman, and Mac Key reported yield improvements of 30-40% over the older varieties in British, American, and Swedish growing conditions, respectively. Regarding individual results obtained from canopy modification studies carried out in oats, shading plus the removal of the flag leaf and/or lower leaves resulted in a reduced grain yield due to a limited supply of assimilates. Efficient interception of solar radiation results from several compatible leaf characteristics, which change in synchrony according to the requirements of the sinks.