Cut ends off of zucchini and slice longways about a quarter inch thick. Repeat with all zucchini and lay flat on a cutting board or large clean surface.
Sprinkle both sides of zucchini with salt and pepper.
In a small bowl mix olive oil and lemon juice. Baste both sides of zucchini with mixture.
Heat your grill to medium-high heat. Lightly oil grill to prevent sticking.
Place zucchini on grill and cook for a few minutes or until you see nice grill marks. Flip over and cook until you have nice grill marks on the other side.
Remove zucchini from grill and serve with a sprinkle of chopped green onion (optional).