I just finished doing this and it was not trivial. In the end this was the approach which worked for me:

Configurable Options in Related Products - Fatal error: Call to a member function getAttributeCode() on a > non-object

(although I spent some time calling the form option block as its own seperate block whereas weddar copy pasts the add to cart options form directly into configurable.php) If you follow his posts, he runs into an issue with undefined renderers which i solved based on this post:

http://inchoo.net/magento/display-html-code-blocks-of-product-options-in-magento/

And using the top comment by fassl to get it working with 1.9

I just finished doing this and it was not trivial. In the end this was the approach which worked for me:

Configurable Options in Related Products - Fatal error: Call to a member function getAttributeCode() on a > non-object

(although I spent some time calling the form option block as its own seperate block whereas weddar copy pasts the add to cart options form directly into configurable.php) If you follow his posts, he runs into an issue with undefined renderers which i solved based on this post:

http://inchoo.net/magento/display-html-code-blocks-of-product-options-in-magento/

And using the top comment by fassl to get it working with 1.9