Grabovski took a nice pass from Phil Kessel, who tied it in the third period, and stuffed a shot behind Marc-Andre Fleury.
The Maple Leafs improved to 3-24-3 where they trail after two periods. More importantly, they moved within four points of eighth-place Carolina in the Eastern Conference. It was far from the best effort from a tired-looking Toronto team that still managed to improve to 9-2-4 since the All-Star break.
Nikolai Kulemin also scored for the Maple Leafs.
Matt Niskanen and Chris Conner scored for Pittsburgh.
Some bizarre scheduling saw the Penguins play their second consecutive game at Air Canada Centre. They returned to Pittsburgh for a couple days of practice after their 6-5 shootout victory over the Maple Leafs on Saturday night before coming back to Toronto.
This game was nowhere near as fast-paced as the first one. The strain of playing seven straight one-goal games appeared to be catching up with the Leafs, who managed just 10 shots through 40 minutes.
But they were only trailing 2-1 heading to the final period and Kessel tied it just over 5 minutes in. His eighth goal in eight games came off a nifty tip of a point shot from Carl Gunnarsson.
The Leafs were given a fantastic opportunity to avoid another overtime when Ben Lovejoy was penalized for tripping Clarke MacArthur with just over 3 minutes left in regulation. However, they were unable to generate many chances with the man advantage.
Toronto finished 0 for 5 on the power play.
Niskanen opened the scoring for Pittsburgh at 6:52 of the first period with his first goal of the season. Shortly after the Penguins won a faceoff in the offensive zone, he beat goalie James Reimer with a shot from the point.
The Leafs tied it a little over 7 minutes later. Kulemin scored his 23rd of the season with a well-placed wrist shot that eluded Fleury.
Conner's goal at 6:40 of the second period put Pittsburgh back in the lead. The rookie protected the puck while skating around defenseman Dion Phaneuf and slid it between Reimer's legs.
Grabovski missed a golden opportunity to tie the game before the end of the period when he had Fleury beat on a clear breakaway and shot wide. The frustrated center thought about smashing his stick in frustration before holding up.
NOTES: The Penguins have lost 151 man-games to injury since Jan. 1. ... Maple Leafs forward Jay Rosehill was scratched for the second straight game. ... Paul Martin and Tyler Kennedy both returned to the Penguins' lineup from injury. ... Pittsburgh was first overall in the Eastern Conference when Sidney Crosby sustained his concussion Jan. 5. It has gone 11-9-4 since.