A very simple way to allow a view to display as if it were a page in an organic group on your Drupal site: Simply paste the code below in your view's Header or Footer, using the PHP Code input format.
Note: the node ID inside node_load() must be set to the group into which you'd like the view to display. To get this to function perfectly (as of OG 2.1), you might need to apply the patch in this issue on drupal.org: Group theme doesn't display on Views that take group as an argument. (Otherwise the group's custom theme might not get set).
There are some alternative methods to getting views to display inside groups, but this is a quick and easy solution.