He smacked a ninth-inning grand slam to match a career high with seven RBIs in the Triple-A 51s' 10-9 loss Monday to the host Bees.
Vegas faced a 10-3 deficit entering the final frame but a six-run output, powered by Shealy's longball, came up just short.
Shealy, who went 2-for-5, also plated runs with a two-RBI double in the third and a bases-loaded fielder's choice in the seventh.
The 31-year-old slugger -- he was designated hitter and slotted cleanup Monday -- has 12 RBIs over his past three games and a total of 37 in 38 games.
Shealy had a pair of four-RBI games this season, including one Friday against Colorado Springs. He collected seven RBIs and went yard twice while playing for the Rockies' top affiliate against Fresno on June 9, 2006.
Shealy was Colorado's 11th-round Draft pick out of the University of Florida in 2002. He played parts of five seasons in the Majors before electing to sign with Toronto -- his fifth organization -- last February.
Darin Mastroianni, Manny Mayorson and Jason Lane each recorded three-hit games, and the 51s outhit their opponent, 19-13, in the loss.
The Bees' Paul McAnulty, Efren Navarro and Gil Velazquez collected three hits apiece, doing most of their damage against starter Jesse Litsch (0-1).
Salt Lake starter Ryan Ketchner (4-4) allowed two runs on seven hits over the game's first six innings.