McLean Stevenson Harry Morgan, M*A*S*H, TV, 1974-83.    Alan Alda’s Commanding Officer changed in the third season from Stevenson’s Henry Blake to Morgan’s Sherman Potter. Morgan served 180 episodes to Stevenson’s 72. Copyright © 2022 Crawley's Casting Calls. All Rights Reserved. Joomla! is Free Software released under the GNU General Public License.