You're quite limited in places to eat at Horseshoe Bay on Magnetic Island, nonetheless there seems to be some quite good eateries along the esplanade. At the end of the main strip I ate at Marlin Bar Tavern choosing the Marlin beef burger, which came with prawns, cheese, tomato, lettuce and pineapple. The burger was tasty, I didn't expect the pineapple to bring out the flavour in everything else, it gave it a kick and nice tangy-ness. The only negative was the beef patty, it was a bit on the thin side.
If you do get a chance to wander through, do check the interior as it has some cool wall hangings of different kinds of knots or stick your head through the window as they are huge!