Managing Default Sort Order on Product Listing and Category
Note: This manual is for osCommerce v4.
After you accessed the admin area of your website, click on the Settings, Configuration and Product listing tabs. Then click on the Product listing default sort order option. If you click on the Edit button, you can choose between the default sort order options (for example, per price, model, name and so on).
The same can be done while adding/editing a category.