Parsnips can come in many shapes and sizes!  Some can be quite small and spindly whereas others can be huge with a very thick end.  For thick parsnips I generally find I need to cut them once horizontally across the middle, then cut the thin tail end once again vertically, then cut the thick end twice vertically (into quarters).  Thin parsnips might just need to be cut once horizontally and then the thick end cut once vertically and the thin end left as it is.  The main thing is to try to get all the pieces roughly the same size.  You can also cut out the core if it seems very hard and woody.