As a commodore, he was deployed to the North American Station, to provide naval support for an expedition led by General Sir Henry Clinton reinforcing loyalists in the Southern Colonies at an early stage of the American Revolutionary War. He led a naval attack against the fortifications on Sullivan's Island (later called Fort Moultrie after their commander), protecting Charleston, South Carolina. However, after a long and hard-fought battle, Parker was forced to call off the attack, having sustained heavy casualties, including the loss of a ship. He subsequently served under Lord Howe in the invasion and capture of New York City and commanded the squadron that captured Long Island and Rhode Island.