Congress may overturn an executive order by passing legislation in conflict with it or by refusing to approve funding to enforce it. In the former, the president retains the power to veto such a decision; however, the Congress may override a veto with a two-thirds majority to end an executive order. It has been argued that a Congressional override of an executive order is a nearly impossible event due to the super majority vote required and the fact that such a vote leaves individual lawmakers very vulnerable to political criticism.
So in effect the Congress has about as much chance overturning an Executive Order as agreeing to whether they would all agree to order a Pizza or Chinese takeaway.