Lang had earlier in the day taken care of Taffy Brower, 3-and-2. Lang advances to take on seven-time USGA champion Carol Semple Thompson.
Semple Thompson, who finished second to Lang last year, collected a 4-and-3 win over Carolyn Creekmore in the third round. Semple Thompson hung on for a 1-up win over Alison Reifers in the second round earlier in the day.
Cecilia Mourgue D'Algue, the stroke-play medalist, went down in the third round. She was knocked off by Marianne Springer, 4 and 3. Mourgue D'Algue won easily in the second round beating Barbara Byrnes, 6 and 4, at Sea Island Golf Club.
Springer will face Deborah Anderson in the quarterfinals. Anderson pounded Robyn Puckett, 5 and 4, in the third round.
Anna Schultz will take on Patty Moore in Wednesday's quarters. Schultz held on for a 2-up win over Judy Miller, while Moore cruised by Viveca Hoff, 4 and 3. Moore had needed 21 holes to win her second round match, but Schultz was well rested for the afternoon match as she crushed Annette Gaiotti 7 and 6.
The last quarterfinal match will pit Toni Weisner and Marianne Towersey. Weisner won the 18th hole to grab a 1-up win over Nancy Smith in the third round. Towersey downed Sandy Woodruff, 4 and 3, to move into the quarterfinals.
The USGA Senior Women's Amateur is open to female amateur golfers who reached their 50th birthday on or before October 7, 2006, and have a USGA Handicap Index not exceeding 18.4.