Add Quantity Inputs to Simple Products on the WooCommerce Shop Page

content-product.php

<?php
/**
 * The template for displaying product content within loops.
 *
 * Override this template by copying it to yourtheme/woocommerce/content-product.php
 * Adapted from work originally authored by WooThemes
 * @license [<http://fsf.org/>] [GPL 3]
 * @version 1.6.4
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

global $product, $woocommerce_loop;

// Store loop count we're currently on
if ( empty( $woocommerce_loop['loop'] ) ) {
	$woocommerce_loop['loop'] = 0;
}

// Store column count for displaying the grid
if ( empty( $woocommerce_loop['columns'] ) ) {
	$woocommerce_loop['columns'] = apply_filters( 'loop_shop_columns', 4 );
}

// Ensure visibility
if ( ! $product || ! $product->is_visible() ) {
	return;
}

// Increase loop count
$woocommerce_loop['loop']++;

// Extra post classes
$classes = array();
if ( 0 == ( $woocommerce_loop['loop'] - 1 ) % $woocommerce_loop['columns'] || 1 == $woocommerce_loop['columns'] ) {
	$classes[] = 'first';
}
if ( 0 == $woocommerce_loop['loop'] % $woocommerce_loop['columns'] ) {
	$classes[] = 'last';
}
?>
<li <?php post_class( $classes ); ?>>

	<?php do_action( 'woocommerce_before_shop_loop_item' ); ?>

	<a href="<?php the_permalink(); ?>">

		<?php
			/**
			 * woocommerce_before_shop_loop_item_title hook
			 *
			 * @hooked woocommerce_show_product_loop_sale_flash - 10
			 * @hooked woocommerce_template_loop_product_thumbnail - 10
			 */
			do_action( 'woocommerce_before_shop_loop_item_title' );
		?>

		<h3><?php the_title(); ?></h3>

		<?php
			/**
			 * woocommerce_after_shop_loop_item_title hook
			 *
			 * @hooked woocommerce_template_loop_rating - 5
			 * @hooked woocommerce_template_loop_price - 10
			 */
			do_action( 'woocommerce_after_shop_loop_item_title' );
		?>

	</a>

	<?php
		if ( 'simple' == $product->product_type ) {
					remove_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_loop_add_to_cart', 10 );
					add_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_single_add_to_cart', 10 );
				} else {
					remove_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_single_add_to_cart', 10 );
					add_action( 'woocommerce_after_shop_loop_item', 'woocommerce_template_loop_add_to_cart', 10 );
				}
		/**
		 * woocommerce_after_shop_loop_item hook
		 *
		 * conditionally hooked woocommerce_template_single_add_to_cart - 10
		 * conditionally hooked woocommerce_template_loop_add_to_cart - 10
		 */
		do_action( 'woocommerce_after_shop_loop_item' );

	?>

</li>

custom.css

/*
This is the companion CSS to go with content-product.php
If your theme has a place for custom CSS use the snippet below. May not work with all themes
but should serve as an example
 */

#main li.product input {
	float: none;
}