He made his major league debut officiating in the first game of the 1970 National League Championship Series on October 3, when an umpires' strike forced the league to use minor league baseball umpires for the first game of the series before the regular umpires returned for Game 2.
Morgenweck was behind the plate, calling balls and strikes, when Nolan Ryan pitched a 1-0 no-hitter at Anaheim Stadium against the Baltimore Orioles on June 1, 1975. It was Ryan's fourth no-hitter, tying the record held by Sandy Koufax. Morganweck was also the home plate umpire for Dick Bosman's no-hitter on July 19, 1974. 
- Levin, Jay. "His life's calling: balls, strikes", The Record (Bergen County), August 9, 2007. Accessed August 9, 2007.
- "Baltimore Orioles vs California Angels: June 1, 1975 Box Score". Baseball Almanac. Retrieved August 9, 2007.
- "Cleveland Indians 4, Oakland Athletics 0". retrosheet.com. Retrieved December 29, 2012.