Going to the Islanders are forwards Carter Verhaeghe and Taylor Beck, defensemen Tom Nilsson and Matthew Finn, and goaltender Christopher Gibson.
Grabner, 27, is entering the final season of a five-year contract with a salary-cap charge of $3 million. He can become an unrestricted free agent after the season.
Grabner has 95 goals and 155 points in 317 games with the Islanders and Vancouver Canucks. His best season was 2010-11, when he had 34 goals and 52 points in 76 games with the Islanders.
View the up-to-date Toronto Maple Leafs salary cap.