Light your grill to high heat and close the lid. Allow the grill to heat up for 15 minutes.
Brush all sides of the mahi mahi fillets with olive oil and then sprinkle a generous amount of Kosher salt and fresh ground black pepper to each side of the fillets.
Once the grill has gotten nice and hot for 15 minutes, open the lid, reduce the grill to medium-high and place the mahi mahi fillets on the grill over direct heat.
Grill for about 4 minutes (times vary based on your grill). The key is to wait until the fillets naturally release from the grill grates. Gently lift an edge of the fillet with a spatula. If the fish releases without sticking, it is time to flip the fish.
Flip the fillets over to the other side and grill for another 3 - 4 minutes, until the flesh is firm but not overcooked.
Remove the grilled mahi mahi from the grill and server with lemon wedges.