Adjusting rotation on instatiated object clone

Need some help here. Have instantiated a laser beam for my space shooter and sent it flying off into space. The trouble is, it’s not horizontal, but vertical. I’ve tried to adjust the rotation, but nothing seems to work. Is there a trick to it?
Thanks!

GameObject projectile = (GameObject)Instantiate(laserPrefab, shootSpot.position, shootSpot.rotation);
projectile.transform.Rotate( myVector3Rot);