The 1st/95th were engaged at the Battle of Quatre Bras on 16 June 1815, ″Until dark we had very sharp fighting″. Simmons spent the night before Waterloo sleeping on the muddy ground on a bundle of straw, sheltering from the rain under a mud-smeared blanket. During the subsequent battle he was shot through the liver, had two ribs broken and took a bullet in the chest. His watch stopped at 4 pm, the time that he was hit.
He was evacuated to Brussels where he remained convalescing for several weeks. In October he was well enough to travel back to England. He was sufficiently recovered from his severe wounds to rejoin his regiment on 1 January 1816, and served with the British army of occupation in France for nearly three years, returning to England with the 1st Battalion in November 1818.
Simmons subsequently served at home until July 1825 when he accompanied the battalion to Nova Scotia. On 17 April 1828 he was promoted to Captain, at which time he had close to nineteen years' service.
Apart from being awarded the Waterloo Medal, for his service in the Peninsular Campaigns Simmons received the Military General Service Medal with eight clasps.
He retired from the army in 1845, a Battalion Major, after thirty-six years' service, and died in St. Helier, Jersey on 5 March 1858. There is a memorial tablet in the town's St. Saviors Church erected by his widow and he is named on the Rifle Brigade Memorial in Winchester Cathedral.