You should create a model server-side, corresponding to your "very large object".
Then, you can pass it to your JS from your controller using :
public ActionResult YourMethod(string param1)
{
//get your object
return Json(yourObject, JsonRequestBehavior.AllowGet);
}
You can call this method asynchronously from your JS thanks to ajax call :
$.ajax({
url : "@Url.Action("YourMethod", "YourController")",
contentType : "application/json; charset=utf-8",
dataType : "json",
type : "POST",
data : JSON.stringify({param1: "test"})
})