The condition is called chlorosis and is caused by a nutrient deficiency in the tree - primarily iron which aids in production of chlorophyll (green pigment). Most often the trees affected by this condition are those species preferring acidic soil such as Pin Oaks, Dogwoods, Sweetgums or Magnolias.
I find the most common culprits in our area seem to be Pin Oaks or Pin Oak hybrids that were sold and installed as Red Oaks. The leaves look very similar to those of Red Oaks but once they are installed in Dallas/Fort Worth's alkaline soil they cannot absorb iron and turn yellow. Most of these trees succumb to the problem before they get large but some having less of the Pin Oak traits can grow larger before they display yellow foliage.
Solution: For larger trees having less Pin Oak traits it may be most economical to apply regular soil amendments that can neutralize the alkalinity in the soil. This will allow greater iron absorption in the trees. There are a variety of ways to do this and can be handled by an arborist. If the trees are small, the best approach is to remove the trees and start with a true Shumard (Red) Oak that is guranteed by the supplier. This way you will be sure to avoid yellowing problems in the future.