Answer

Within your template.php file enter the following:


function yourthemename_node_form($form) {
// Collapse fieldsets
$form_elements = element_children($form);
foreach ($form_elements as $element) {
if ($form[$element]['#type'] == 'fieldset') { //Identify fieldsets and collapse them
$form[$element]['#collapsible'] = TRUE;
$form[$element]['#collapsed'] = TRUE;
}
}
return drupal_render($form);
}