Delaying Fajr prayer beyond the proper time

If you are praying Fajr prayer before the sun rises, then the
Sunnah in your case is to pray the regular Sunnah of Fajr which is two
rak’ahs. If you miss Fajr and do not wake up until after the sun has risen,
then you should pray Sunnah and then Fard (obligatory prayer). But if you
always delay Fajr prayer until after the sun has risen, this is a serious
problem. In this case, before you ask about the Sunnah prayer you have to
pause and ask yourself what you will say when you stand before Allaah on the
Day of Resurrection, and He calls you to account for neglecting Fajr
prayer. 

See also question no. 266.