'Grate on a coarse grater' means to use the side of your grater with the largest holes to shred the ingredient. This results in thicker, more substantial shreds compared to using a finer grater.
When a recipe instructs you to 'grate on a coarse grater,' it's specifying the size of the shreds you need. A grater typically has multiple sides, each with different sized holes. The 'coarse' side has the largest holes, producing thick, relatively long shreds. This is in contrast to a fine grater, which creates very small, almost powdery shreds. Using a coarse grater is often preferred when you want the ingredient to retain some texture and be easily identifiable in the final dish. For example, coarsely grated cheese melts differently than finely grated cheese, and coarsely grated vegetables add more bulk and bite to a salad. To grate, hold the grater firmly and run the ingredient along the coarse side with even pressure, being careful to avoid grating your fingers.
To prevent the ingredient from sticking to the grater, lightly spray the coarse side with cooking oil before you begin. This will make grating easier and cleanup faster.