Cold weather brake problems

I had this happen on my 2011 Outback Sport this morning.  Scared the crap out of me.  4 degrees outside, with colder wind chill.  Backed car out of driveway, found brakes to be "frozen" (very little play in pedal, very little braking action).  They became responsive almost immediately after putting the gear in drive, however.  Car is 4 years old, with 53,000 miles.  I guess a stop at the repair shop is in order.  At least now I know what to tell them to look for!