The 20-year-old, who will turn professional and play in the Scandinavian TPC Championship in Sweden next week, had a flawless seven-birdie round to move one shot clear of American Cristie Kerr. "I would have turned professional this week, but I qualified through winning the British Amateur in June," she explained.
After yesterday's wild and windy conditions, Stahle was relieved to encounter a relatively still day. "It was much easier and I made all the putts I needed," she said.
Stahle has spent the last year at Arizona State University, won three times on the college circuit and was named the US college player of the year and is tipped for a great future in the professional ranks.
Kerr also had a flawless round. She started by holing a 65-foot putt for birdie at the first and made more at the second, fifth and seventh in an outward half of 31.
She then had a run of pars before signing off with fours at the par-five 17th and 18th.
A winner of the Michelob Ultra Open in Virginia in May, the 27-year-old from Miami admits she loves the British courses but she was relieved that the weather had eased.
"I shot one over yesterday and it felt more like three under," she said.
"But the conditions did help me stay focused. These links courses are such a great challenge."
Karen Stupples, the defending champion from Kent added a 71 to her opening 74 to stand on one over for the championship while Laura Davies, the 1986 champion, was another Briton certain to make the cut after a 70 for two over 146.
Catriona Matthew, out in the early afternoon, was the best of the British players on one over par overnight, but she dropped a shot at the second to slip to two over, while playing partner Michelle Wie, the 15-year-old American amateur, birdied the same hole to also stand on two over.
World number one Annika Sorenstam was another late starter and opened with a couple of pars.
Leading first-round scores in the Women's British Open, Royal Birkdale (GB and Irl unless stated). 68 Jang Jeong (S Kor). 69 S Gustafson (Swe). 70 - N Perrot (Ch). 71 L Neumann (Swe), K Williams (US), E Klein (US), S Sandolo (It), M Dunn. 72 Ai Miyazato (Jap), L Wessberg (Swe). 73 P Marti (Sp), C Matthew, A Sorenstam (Swe), L Stahle (Swe), C Kerr (US), L Kane (Can), H Hee-Won (S Kor), A Carlota Ciganda (Sp), P Meunier-Lebouc (Fra), A Monke (Ger), R Higashio (Jap). 74 S Steinhauer, M Nagl (Bra), Kim Young (S Kor), J Inkster (US), L Diaz (US), K Stupples, H Bowie (US), B Burton (US).
l The Welshman Bradley Dredge hit 63 to lead the Scandinavian Masters in Stockholm after the second round yesterday. Dredge recorded nine birdies and one bogey at the Kungsangen course to finish 13 under par at the halfway stage, one shot clear of England's Barry Lane and the Swede Pierre Fulke. Another Swede, Henrik Nystrom, and the Frenchman Jean-Francois Remesy were a shot further back on 11 under. Another Henrik, Norway's Bjornstad, and Marc Cayeux of Zimbabwe were on 10 under.