Buller went ashore during the Peace of Amiens, and was elected as Member of Parliament for East Looe in 1802, but with the outbreak of hostilities again in 1803, was appointed to the 80-gun and employed in the blockade of the French and Spanish Atlantic ports. He was made a Colonel of Marines on 28 April 1805, and was assigned to the fleet under Sir Robert Calder and took part in the Battle of Cape Finisterre on 22 July 1805. During the battle Buller found himself isolated from the rest of the fleet due to the patchy fog and failing light, and was surrounded by five enemy ships. He fought them off, forcing the Spanish 84-gun "San Rafael" to strike, and afterwards sending the "Malta"s boats to take possession of the Spanish 74-gun "Firme". "Malta" had suffered considerably during the battle, having her mizzen top mast and mizzen sail yard shot away, and her mizzen and main masts damaged. Her rigging and sails were cut up, with her casualties amounting to five dead and forty wounded.