Magento – Display Out of Stock Simple Products swatches in configurable product

Set the simple product Visibility (Catalog->Manage Product->"Select Product"->General) to "Not Visible Individually". Place the simple product to "In Stock" and add Quantity. (Simple products will not show on the front end)

The Configurable product should now show the available simple products. A configurable products inventory is based off the simple product's inventory.

Hope this helps.

Goto

Mage / Catalog / Block / Product / View / Type / Configurable.php

public function getAllowProducts()
{
    if (!$this->hasAllowProducts()) {
        $products = array();
        $skipSaleableCheck = Mage::helper('catalog/product')->getSkipSaleableCheck();
        $allProducts = $this->getProduct()->getTypeInstance(true)
            ->getUsedProducts(null, $this->getProduct());
        foreach ($allProducts as $product) {
            if ($product->isSaleable() || $skipSaleableCheck) {
                $products[] = $product;
            }
        }
        $this->setAllowProducts($products);
    }
    return $this->getData('allow_products');
}

Replace with this

public function getAllowProducts()
{
    if (!$this->hasAllowProducts()) {
        $products = array();
        $skipSaleableCheck = Mage::helper('catalog/product')->getSkipSaleableCheck();
        $allProducts = $this->getProduct()->getTypeInstance(true)
            ->getUsedProducts(null, $this->getProduct());
        foreach ($allProducts as $product) {
            $products[] = $product;
        }
        $this->setAllowProducts($products);
    }
    return $this->getData('allow_products');
}

Note: Don't Edit in Core files. Make rewrite or copy the folder structure in to local code pool.

Cheers.