Out of the box ATG eCommerce does not support product bundles. It does support SKU bundles, i.e. a product can consist of multiple SKU’s.
To support product bundles is pretty simple to implement.
First you create a new type of product for bundles in /atg/commerce/catalog/productCatalog.xml.
Then you define your bundles product to have the new products property. This property is simply a list of products that the bundle contains, e.g. Costco organic cotton polo shirt and Nike athletic shorts.
A few years ago I did a more advanced version of this implementation which allowed for different numbers of products in one bundle, e.g. two different kinds of shirts and one pair of pants. I did this using the concept of product links which is similar to SKU links that ATG supports.
If you are interested in wanting to implement a more advanced version please contact us.