I agree with CarlRJ - the correct solution would be to use a better text editor. E.g. TextWrangler can deal with very large files with no problem.
TextEdit is a good choice for a (simple) word-processor, but not so good for a text-editor (for plain text files).

Maybe it's improved in recent years, but I once tried opening a large file in TextWrangler, and it just hung there, assumedly trying to load the whole thing into memory. I ended up learning to use emacs enough just to read it, which worked fine. I'm sure less or vim would work just as well.

One could argue that these command line tools have a much better legacy and hence are more stable with respect to these things. Or perhaps the fact that they only have to render one terminal screen at a time gives them a better loading model (it's hard for a GUI editor to dynamically load different parts of a file into memory when they all live in the same scroll area).