Vernon County operated with the Amphibious Forces of the United States Atlantic Fleet, alternating between Norfolk, Virginia, and Little Creek as her home ports.

In 1958, Vernon County was transferred to the United States Pacific Fleet, sailing via the Panama Canal to her new assigned home port, San Diego, California.

After her return to Yokosuka and subsequent refresher training at Numazu, Japan, Vernon County took part in Operation Litgas in company with other SEATO naval units.

Over the ensuing months, Vernon County conducted various operations: loading, offloading, stand-by alerts, and the landing of and equipment on South Vietnamese shores.

While Vernon County was carrying out those duties, American military intelligence picked up evidence that a Viet Cong (VC) force was massing for an attack on Chu Lai.

Starlite thwarted the incipient VC move toward Chu Lai, some nine miles (14.5 kilometers) to the north, the main battle taking place in the Van Truong village complex.

The Marines discovered communication equipment, numerous documents, munitions, rice, and propaganda – all leading intelligence men to estimate that the hamlet of Van Thuong had served as a VC command post.

After operating locally out of Yokosuka and in South Vietnamese waters, primarily at Chu Lai, Vernon County replenished and underwent a period of upkeep at Subic Bay in the Philippines.

Completing those repairs and alterations on 15 March 1967, Vernon County ran sea trials and conducted refresher training before visiting Kobe in April 1967.

Vernon County remained in port at Yokosuka until 5 October 1967, when she headed south for Ora Bay, Okinawa, to conduct two days of training with U.S. Marine Corps amphibious forces.

In that operation, U.S. Marines from the group landed, unopposed, and swept through the sandy, marshy regions north of the Cửa Việt Base, encountering several pockets of enemy resistance.

Vernon County, when relieved of duty with TG 76.5, headed for Japan and returned to her home port of Yokosuka for a scheduled two-month overhaul, after which time she sailed for Korean waters.

Offloading her cargo at Wunder Beach, Vernon County shifted operations to the Mekong Delta region, where she assumed the duty of support LST for mobile riverine forces.

During that period, the group operated at Bến Tre, Dong Tam Base Camp, Vĩnh Long, Sa Đéc, Mỹ Tho, and Cần Thơ, all in the Mekong Delta, or IV Corps, area of South Vietnam.

Vernon County served as a floating warehouse wherein 600 tons of ammunition, plus non-ordnance support material, could be stowed in the capacious tank deck area.

Sailing to Kaohsiung, Taiwan, with a cargo of jeeps, and encountering Tropical Storm Hester en route, Vernon County visited Hong Kong for rest and recreation before returning to Yokosuka in late October 1968.

The action on the part of Vernon County, described as "quick and professional",[1] resulted in 27 letters of commendation and a Bronze Star for the ship's sailors who participated in the salvage operation.

Vernon County carried out training activities in the days that ensued, lifting 185 field troops from E Company, 2nd Battalion, 26th Marines, from Chu Lai to Da Nang.

Reaching Da Nang on 4 November 1969, Vernon County embarked 147 Marines of the Headquarters and Service Company, 9th Motor Transport Battalion, 53 vehicles, and 58 tons of equipment.

Vernon County suffered storm damage – two perpendicular cracks began to develop on opposite sides of her mast, directly below the radar platform.

Vernon County returned to South Vietnam soon thereafter, initially to Vũng Tàu, where she took on a load of ammunition to be delivered to tank landing ship supporting Task Force 115's riverine operations.

Necessary upkeep items, however, could only be completed by Vernon County and gunboat USS Welch, which then proceeded to sea as scheduled to resume the transit to Cam Ranh Bay.

Her responsibilities and activities generally similar to those of previous Market Time deployments, Vernon County remained on station supporting Task Force 115 until 5 November 1970.

During the week of 7 February 1971, the final preparations were made for Vernon County to become, by necessity, totally self-sufficient, far from the U.S. Navy's logistic, maintenance, and support areas.

After taking on part of the necessary stores and equipment, she sailed for Okinawa to pick up the rest before proceeding on her way, bound for remote Diego Garcia, in the Chagos Archipelago in the British Indian Ocean Territory, with an interim stop at Singapore.

Later, having established a self-sustaining shore party, Vernon County made two additional voyages to and from Diego Garcia, picking up more men and supplies at Singapore, Cocos Island, and Mauritius.

During the last few days of her deployment to Diego Garcia, Vernon County was repainted her standard haze gray, a sure sign that the time had come for the ship to sail away from the atoll upon which she had established a base camp and the beginnings of a communication station.

Vernon County conducted another tour of duty in South Vietnamese waters in the summer of 1971, again performing the duties of Operation Market Time support ship, a job that entailed her staying close to shore and serving as a landing platform for helicopters, a haven for patrol boats, and a supplier of food, fuel, water, lodging, and ammunition for both helicopters and patrol craft.

After completing repairs to the fishing craft's engine, Vernon County's men received a present of four boxes of fresh crabs and squid in grateful appreciation of the services they rendered.

Vernon County ultimately spent the remainder of her active naval career in the Far East, returning twice more to South Vietnamese waters and serving once more as Operation Market Time support LST.