o3dConverter can read COLLADA files as either DAE text files (and associated asset files in subdirectories), or as part of a ZIP archive (or KMZ file).
In addition, o3dConverter outputs a gzip-compressed tar archive (.tgz) which contains a JSON file and any associated assets (textures, shaders, etc.) from the source COLLADA model.
Optionally, you can output a set of flat files into a directory, which is the layout compatible with the WebGL implementation of O3D.
o3dConverter is cross-platform and it works on Mac OS X and Windows. Binaries for the Windows platform are available on the project's homepage.
Detailed instructions on how to install and use the o3dConverter utility on your Mac are available HERE.