After serving only one term, the 22nd Canadian Parliament, he was defeated by Jake Schulz of the Co-operative Commonwealth Federation in the 1957 election.
Weselak made a further attempt to win back the seat in the 1958 election but lost to Val Yacula who unseated Schulz.
When Yacula died shortly after that victory, Weselak was again unsuccessful in a December 1958 by-election campaign.
During the 1956 Suez Crisis, Weselak was part of Lester B. Pearson's delegation to the United Nations.
Pearson was then External Affairs minister under the Louis St. Laurent government, and his efforts led to the formation of United Nations peacekeeping force which defused a full-scale Middle Eastern war.