I really would like to avoid having to install virtual box just to use Oracle 11g. Is there a way to install it into Mac OSX?
Oracle Database 11g runs only on Windows, Linux, Solaris, HP-UX or AIX.
If you want to run it on a Macintosh, it must be running one of the supported operating systems.
So you either must reboot to a supported OS with BootCamp or install a virtualized OS with VirtualBox, VMware Fusion or something else.
Please see the detailed instructions for accomplishing this on Stack Overflow:
You won't need a permanent virtualized installation, but it is necessary for the initial install.