First timer to Spain and I'm driving with my wife, daughter and brother-in-law from Oviedo to Madrid.
Any hints on who to toss out 3 hours into the drive? Just kidding...
Can someone give me an idea of driving conditions around March 26, i.e, chains required thru the mountains, etc?

I've done this drive by motorway and assuming this is your route I would be extremely surprised if you have any problems at all. The bit from Oviedo to Leon is through mountains but the motorway is very well maintained and usually kept clear. It's also extremely pretty. From Leon to Madrid is the opposite (straight, flat, etc but roads still good) except the Sierra just outside Madrid.

Re the first part, tough choice, depends on what the brother in law is like. If the mother in law was there too then there'd be no choice to make of course.

For information about driving conditions check out Dirección General de Tráfico website.

Another great website (in Enlish) is Vía Michelin @ http://www.ViaMichelin.com/ . This site gives driving directions, times, distance, maps, etcetera. Really excellent.

Saludos, MadridMan