Draw RenderTexture to Camera with Graphics.DrawTexture

DrawRT.cs

using UnityEngine;
using System.Collections;

// attach this scrip to the camera you want to draw your rt from elsewhere
public class DrawRT : MonoBehaviour
{
    public RenderTexture rt; // render to this rt from another camera

    Camera cam;
    Rect cameraViewRect;

    void Start()
    {
        cam = GetComponent<Camera>();
        cameraViewRect = new Rect(cam.rect.xMin * Screen.width, Screen.height - cam.rect.yMax * Screen.height, cam.pixelWidth, cam.pixelHeight);
    }

    // works
    
    void OnGUI()
    {
        //if (Event.current.type.Equals(EventType.Repaint))
    //    { 
            //Graphics.DrawTexture(rect, rt);
  //      }
    }

    // works, if have ongui method included
    IEnumerator OnPostRender()
    {
        yield return new WaitForEndOfFrame();
        Graphics.DrawTexture(cameraViewRect, rt);
    }

    // doesnt work
    /*
    void PostRender()
    {
        Graphics.DrawTexture(rect, rt);
    }*/
}