With (native) Windows NT 4+ commands:

    NET LOCALGROUP Administrators

Or, to remove header and footer lines:

   FOR /F "delims=[]" %%A IN ('NET LOCALGROUP Administrators ˆ| FIND /N "----"') DO SET HeaderLines=%%A
   FOR /F "tokens=*"  %%A IN ('NET LOCALGROUP Administrators') DO SET FooterLine=%%A
   NET LOCALGROUP Administrators | MORE /E +%HeaderLines% | FIND /V "%FooterLine%"