2008-09: Appeared in 33 games for the Bulldogs (aka Elis) as a freshman, leading the team in rookie scoring with 26 points (12 goals, 14 assists). His 29 assists also co-led the Elis. O'Neill finished the season leading all rookies in goal scoring with ten and ranked tied for second in points with 17 in 21 conference games en route to earning a spot on the ECAC All-Rookie team. O'Neill was twice named the ECAC's Rookie of the Week (January 12 and March 3). He was also named to the ECAC's All-Academic Team as well.
2009-10: Brian O'Neill was the leading scorer for ECAC Hockey regular season champion Yale as a sophomore. Though somewhat overshadowed by 27-goal scorer Broc Little, O' Neill scored 16 goals with 28 assists and was plus-13 playing on a line with Andrew Miller and Dallas free agent signee Sean Backman. O'Neill scored 6 of his 16 goals on the Bulldogs' power play. Yale dominated the regular season but were upset by Brown in a three-game ECHL Hockey quarterfinal series. The Bulldogs rebounded to defeat North Dakota in the NCAA Northeast Regional for the team's 21st win of the season before falling to eventual national champion Boston College in a wild 9-7 game in the Northeast Final.
2010-11: O'Neill led Yale in both goals and points in his junior season as the Bulldogs dominated ECAC Hockey for most of the year; finishing second to Union and then rolling through the playoffs. One of eight players on Yale with 20 or more points, O'Neill scored 20 goals with 26 assists and was plus-13 with 26 penalty minutes in 36 games. Ten of his 20 goals were scored on the Yale power play. The Bulldogs got off to a 15-1 start before losing three games in a five-game stretch (including one loss to Union). In the ECAC Hockey tournament the Bulldogs had back-to-back-shutouts in the semifinal and championship games and then defeated Air Force in an NCAA East Regional game. For the second year in a row Yale lost to the eventual national champion in a regional final; falling 5-3 to Minnesota-Duluth.
2011-12: O'Neill signed a one-year free-agent contract with the Kings in March 2012 following his senior season at Yale and made his pro debut with AHL Manchester. He scored 1 goal with 1 assist and was plus-three with 4 penalty minutes in 12 games for the Monarchs. Manchester finished second in the Atlantic Division and lost to Norfolk three games to one in a first round playoff series. O'Neill skated in all four playoff games and was minus-two with 1 assist and 6 penalty minutes. O'Neill led Yale in scoring for the third straight year, proving capable of scoring even with Little having graduated. He scored 21 goals with 25 assists and finished plus-16 with 37 penalty minutes. He was named to the ECAC First All-Star and NCAA East All-American teams. Yale slipped to sixth in ECAC Hockey and lost a three-game series to Harvard in the conference quarterfinals.
O'Neill is a small, quick forward blessed with excellent offensive instincts. He possesses great finishing ability and during his collegiate career at Yale showed to be most dangerous below the dots. He can control the tempo of a game and simply makes things happen whenever he's on the ice. His great hands and vision also makes him an outstanding playmaker as well. While O'Neill played almost exclusively at right wing in his final two years at Yale, he has demonstrated to be equally adept playing left wing, where he spent much of his first two years playing.
O'Neill is an excellent skater with a good burst of speed, but he is more about quickness. That can be seen in his great transitioning and puck-moving ability. He makes good decisions with the puck too. Two of O'Neill's greatest assets are his remarkably accurate shot and blistering release.
One of the unique aspects of O'Neill's game is his grittiness. He plays with a great deal of physicality for a player that is 5'9"/175 lbs. and can lay out some solid checks, even against bigger opposing players. He works hard, is a tough competitor, and can be quite difficult to defend against. Where this is particularly evident is in his play along the boards and in the corners.
While O'Neill has the skill set to play at the pro level, he will need to continue to add size and strength to his 5'9" frame to be successful.