Only if you keep OS 9 on the machine. I run OS 9 on another partition, though you can load both on the same one. I never have.
OS 9 will run through OS X's Classic, but Quark is simply awful running through Classic. Pages won't redraw without collapsing them, and sometimes even window-shading the page with a double click doesn't fix it.
There are Quark extensions available for free that supposedly prevent the redrawing problem. I use RedrawClassic XT US, which I found to the best of a bad lot, but the problem remains. I simply boot into 9 to use Quark.