How to customize the markup of radio buttons in the edit/create node view?
You can alter the output by overriding the following Drupal theme functions: theme_form_element, theme_radios, and theme_radio. (You won't need theme_radio unless you want to make changes to the &lt;input&gt; tag.)

Copy these functions into your theme's template.php file and replace "theme" in the function name with the name of your theme. Customize as needed. You will have to clear your cache in order for the changes to take affect.

In theme_form_element(), if you want to limit your changes to radio elements, you can add this condition:



if ($element['#type'] == 'radios' || $element['#type'] == 'radio') {
  // your stripped down mark-up here
}
else {
  // default mark-up
}


You can also check against other criteria such as #name and #id:



if (strpos($element['#id'], 'edit-group-content-access') !== FALSE) {
  // This form element has an id of 'edit-group-content-access-und-1' or 'edit-group-content-access-und-2'.
}  


A real world example that only prints the wrapper for elements that ARE NOT radio elements (only alter the code that is shown and leave the rest as-is):

BEFORE



function mytheme_form_element($variables) {
  // ... 
  $output = '&lt;div' . drupal_attributes($attributes) . '&gt;' . "\n";
  // ...
  $output .= "&lt;/div&gt;\n";
  // ...
}


AFTER



function mytheme_form_element($variables) {
  // ... 
  $output = '';
  if ($element['#type'] != 'radios' &amp;&amp; $element['#type'] != 'radio') {
    $output = '&lt;div' . drupal_attributes($attributes) . '&gt;' . "\n";
  }  
  // ...
  if ($element['#type'] != 'radios' &amp;&amp; $element['#type'] != 'radio') {
    $output .= "&lt;/div&gt;\n";
  }  
  // ...
}


Bonus tip :): If you just want to alter the attributes of the wrapper, not remove it entirely, see this example.