He finished his NHL career with brief stints with the Colorado Rockies and Detroit Red Wings, and spent two seasons in the minor leagues before retiring as a professional in 1985.

During summers in his childhood, Weir attended Glen Sather's hockey school 200 miles from his hometown Ponoka in Banff, Alberta.

In the 1969–70 season, Weir amassed 35 goals and 26 assists in only 42 games, earning him the Ernie Love Trophy (given to the AJHL Scoring Champion) at the age of 17.

The following season saw Weir join the Medicine Hat Tigers of the Western Hockey League and win the WCHL Rookie of the Year.

Weir played hard for the Oilers scoring 57 points in his first 42 games and made some headway when he was called back up to rejoin Toronto at the end of the season and into the playoffs.

Knowing Toronto was expecting more out of him and that he might again be sent to the minors, Weir decided to jump to the World Hockey Association and join the Edmonton Oilers to play on a premiere team.

When the Oilers joined the NHL the following season, Weir was first claimed back by Toronto before the expansion draft but was then reacquired on waivers by Edmonton a few weeks later.

After already playing in 10 games for Colorado, the NHL voided the trade after Cooper was found to be hiding injuries and Weir was returned to Edmonton.