After a dominant collegiate hockey career at St. Lawrence University, capped by being selected to the ECAC First All-Star Team in 1968, Croteau was signed as a free agent by the Toronto Maple Leafs in 1968, which promptly dealt him to the Los Angeles Kings. He played two sound seasons with LA's American Hockey League Springfield Kings farm team, and in limited action with Los Angeles in 1968 scored a fine five goals in eleven games. On the strength of that performance, he played with the Kings in the playoffs that year, scoring five goals in eleven games as Los Angeles went to the semifinals. Before he could play further for the Kings, he was dealt to the Detroit Red Wings February 1970, seeing only limited action with Detroit before being claimed by the California Golden Seals in the 1970 waiver draft. With the talent-thin Golden Seals, he became a regular for four seasons, finishing among the team's leading scorers in his first and final seasons with the squad.
When the NHL expanded to Kansas City and Washington in 1974, Croteau was the seventh pick of the Scouts  and a key player for the weak franchise from the beginning. After a modest 1975 season, Croteau was one of the team's leading scorers and few decent players for four years thereafter, even after the franchise moved to Denver and became the Colorado Rockies in 1976. His best season came in 1977, when he scored 24 goals and 27 assists for 51 points, all career highs.
After an injury that cost him most of the 1980 season, Croteau retired from hockey, save for a brief stint in the minor leagues the following year.
Croteau finished his career with 144 goals and 175 assists in 688 games for 319 points, adding 143 penalty minutes.
Awards and honors
|All-ECAC Hockey First Team||1967–68|
- Gary Croteau's career statistics at The Internet Hockey Database
- Gary Croteau's biography at Legends of Hockey
|Colorado Rockies captain