BundleConfig.cs

using System.Web;
using System.Web.Optimization;
using BundleTransformer.Core.Transformers;

namespace Project {

  public class BundleConfig {

    	public static void RegisterBundles(BundleCollection bundles) {

			var styles = new Bundle("~/bundles/stylesheets")
				.Include("~/Assets/stylesheets/*.css")
				.Include("~/Assets/stylesheets/*.less");
			styles.Transforms.Add(new CssTransformer());

			bundles.Add(new ScriptBundle("~/bundles/javascripts").IncludeDirectory("~/Assets/javascripts/plugins", "*.js").IncludeDirectory("~/Assets/javascripts", "*.js"));
			bundles.Add(styles);
		}
	}
}

Global.asax.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Hosting;
using System.Web.Http;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;

namespace Project {

  public class MvcApplication : System.Web.HttpApplication {

    	protected void Application_Start() {

			FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
			RouteConfig.RegisterRoutes(RouteTable.Routes);
			BundleConfig.RegisterBundles(BundleTable.Bundles);

		}
}

Site.Master

<%= Styles.Render("~/bundles/stylesheets") %>
<%= Scripts.Render("~/bundles/javascripts") %>

Web.config

<configuration>
	<bundleTransformer xmlns="http://tempuri.org/BundleTransformer.Configuration.xsd">
  		<core>
			<css>
				<minifiers>
					<add name="NullMinifier" type="BundleTransformer.Core.Minifiers.NullMinifier, BundleTransformer.Core" />
				</minifiers>
				<translators>
					<add name="NullTranslator" type="BundleTransformer.Core.Translators.NullTranslator, BundleTransformer.Core" enabled="false" />
				<add name="LessTranslator" type="BundleTransformer.Less.Translators.LessTranslator, BundleTransformer.Less" /></translators>
			</css>
			<js>
				<minifiers>
					<add name="NullMinifier" type="BundleTransformer.Core.Minifiers.NullMinifier, BundleTransformer.Core" />
				</minifiers>
				<translators>
					<add name="NullTranslator" type="BundleTransformer.Core.Translators.NullTranslator, BundleTransformer.Core" enabled="false" />
				</translators>
			</js>
		</core>
	    <less>
	      <jsEngine name="V8JsEngine" />
	    </less>
	</bundleTransformer>
	<jsEngineSwitcher xmlns="http://tempuri.org/JavaScriptEngineSwitcher.Configuration.xsd">
		<core>
			<engines>
				<add name="V8JsEngine" type="JavaScriptEngineSwitcher.V8.V8JsEngine, JavaScriptEngineSwitcher.V8" />
			</engines>
		</core>
	</jsEngineSwitcher>
</configuration>