I found some info about the Monterrey Oak at Howard Garrett's website. Apparently they are considered semi-deciduous in Zone 8.

Here is a link that might be useful: Dirt Doctor Mexican White Oak info

I have 4 Monterrey Oaks and I love them. It is not unusual for their leaves to start to turn brown and lose their leaves. I mowed yesterday and noticed a few on the ground. Last year my trees started to lose leaves around the middle of February. The first few years I had these trees, I just knew they were dying....not so!
Don't panic....they should be just fine. They give great shade and are a very beautiful tree. Another plus is they're resistant to oak wilt disease and drought tolerant/resistant! You need drought tolerant/resistant in TEXAS!

Thanks guys! I appreciate the reassurance, and I'll let my friend know. Thanks again for the feedback!

Heather

They are like Live Oak. They drop old leaves mid-late winter and grow new ones a bit earlier than Live Oak. Grows pretty fast.