Park downed stroke-play medalist In-Kyung Kim, 3-and-2. Alison Whitaker held off Maria Uribe, 1-up, to move on to the semifinals where she will square off against Maru Martinez. Martinez needed 19 holes to down Jenny Suh.
Pressel, the co-runner-up at this year's U.S. Women's Open, got off to a hot start by birdieing three of the first four holes at the Settindown Creek Course at Ansley Golf Club to take a 3-up lead.
Lee fought back with a birdie of her own at the fifth to get within 2-down. Pressel, who defeated Jane Rah in the third round, birdied the seventh to regain her 3-up cushion.
Around the turn, Pressel birdied 10, 11 and 12 to stretch her lead to 6-up with six holes to go. Lee birdied the 13th, but Pressel matched that with a birdie of her own to close out the match.
'Today I played really well,' Pressel said. 'I just played consistently, very solid.'
Park, who was a 3-and-1 winner over Nannette Hill in the third round, took an early 2-up lead with a birdie on the second and a bogey by Kim at the third.
Kim birdied the par-5 fourth, but Park birdied five and six to move 3-up. Park later extended that lead to 5-up with birdies on nine and 11. Kim started to get back into the match with Park's help.
Park bogeyed the 12th and 14th as her lead dropped to 3-up. Park struggled to a double-bogey on the 15th. However, she managed to close out the match with a birdie on No. 16.
'I feel great. I mean, I don't think I ever putted that well before,' said Park. 'I came out here probably two or three hours before my tee time and started putting. I knew it was going to be a tough match and I knew she is a really good player.'
Uribe and Whitaker battled in a close match throughout their 18 holes. The duo halved the first four holes with pars. Uribe finally gained a 1-up lead at the fifth when Whitaker tripped to a bogey.
They both parred the next five holes. Whitaker squared the match at 11 with a birdie. Uribe stumbled to a bogey on No. 14 to fall 1-down. Whitaker birdied the 16th to move 2-up. She faltered to a bogey at the next, but halved the last with a birdie to take the match, 1-up.
Martinez, who romped to a 7-and-6 win over Virginia Grimes to move into the quarterfinals, and Suh halved the first six holes. Martinez birdied seven and eight, but bogeyed the ninth to make the turn 1-up. Suh and Martinez swapped bogeys on 13 and 14.
Another bogey by Martinez on the 15th squared the match. Suh birdied the next to take her first lead, but Martinez birdied the 18th to extend the match. Martinez came right back with a birdie on the par-5 first to win the match.
The 18-hole semifinal matches will take place on Saturday, while the 36-hole final will be played on Sunday.