Complex sentence: Olson served as leader of the opposition in the Senate in 1979 and returned to Cabinet when the Trudeau Liberals returned to power in 1980 serving as Minister of Economic and Regional Development from 1980 to 1984 as well as Leader of the Government in the Senate.
Split into simpler sentences: Olson served as leader of the opposition in the Senate in 1979, and returned to Cabinet when the Trudeau Liberals returned to power in 1980. He served as Minister of Economic and Regional Development from 1980 to 1984, as well as Leader of the Government in the Senate.