We need to see photos of the trees, what kind of oaks they are and where and when they were planted.

Because many types of oaks hold their leaves well into winter, they can sometimes appear dead looking. There are also other issues that can affect the health of oaks so that is a possibility as well. But without photos to illustrate and more of an explanation, we can't possibly make any assessment of what's happening.

Also add your general location in the world please, since some disease or pest issues are regional or effect certain species. So I am in central NH and have different trees and issues than my sister in the Bay Area in CA or my brother in the Denver area.