As an advanced college bat, McBroom figured to move quickly through the Toronto system, and he debuted in 2014 with the Vancouver Canadians as one of the older players in the league. In the short season North Western League that season, McBroom showed great power by blasting 11 home runs driving in 59 runs while batting .297 to earn mid-season all-star honors. He also added 23 doubles in those 70 games.
After an impressive pro debut, McBroom built off of that remarkable showing in the Midwest League with the Lansing Lugnuts in his first full season. In 127 games with Lansing, McBroom batted .315 with 39 doubles, 12 home runs, and 90 RBI. His hot season earned him league MVP honors when all was said and done.
McBroom moved up to High-A Dunedin in the Florida State League to open 2016, and he picked up right where he left off in his 2015 MVP season. In a league where power numbers are low, McBroom crushed 21 home runs and added 26 doubles to go along with 83 RBI and a .274/.323/.468 slash line. His numbers earned him a brief nine-game promotion to Double-A New Hampshire to close out the season. McBroom was honored as both a mid and postseason Florida State League all-star.
In his first full-season in the upper levels of the minor leagues, McBroom slashed 243/.321/.402 with 19 doubles, 12 home runs, and 54 RBI in 96 games with New Hampshire and was named an all-star for the fourth consecutive season before being traded to the Yankees. McBroom was already in Trenton when the trade was consummated and had to walk a few feet down the hall to join his new teammates in the home clubhouse. In 38 games for the Thunder following the trade, McBroom slashed .257/.327/.379 with four homers and 16 RBI.