Forbes and Doolan finished the day on 138, eight under par and one stroke ahead of six players including two more British challengers, Dale Reid and Claire Duffy.
Forbes, who defends her French Open title next month, had only one lapse. She took three putts on the second green for her only bogey of the day but made amends with birdies at four of the five long holes.
Early morning fog delayed the start of play for two hours and Reid, from Scotland, only just managed to finish before darkness closed in.
She was seven under at the turn but then dropped three strokes in four holes when turning for home. She came back with a late burst of three birdies in her last five holes to edge to within one stroke of the lead.
In unusually wintry conditions at in St Louis, Missouri, Sweden's Annika Sorenstam carded 69 to finish one shot behing Tracy Hanson, whe led after the first round of the the Heartland Classic. The defending champion Liselotte Neumann, also of Sweden, shared third place on 70 with Kim Williams.
England's men retained their home international title at Royal Portrush yesterday when crushing a below-form Scotland by 91/2 points to 51/2. The holders overcame defeat yesterday against outsiders Wales to prevail narrowly on countback.
England, captained by the former British amateur champion Peter McEvoy, took the title by just 1/2pt, edging out Ireland 25-241/2. It was their 26th overall victory in the series, first contested in 1932, and their fourth hat-trick.
McEvoy believed his side was the strongest line-up entering the contest, and they proved that. The standard in the final singles meeting was superb over the Antrim course.
The all-Walker Cup meeting between Broome Manor's David Howell and Cochrane Castle's Barclay Howard was won by England's Howell by 4 and 2 after he covered the course in seven under par.
McEvoy said: "The first day was horrendous - we played really poorly. But all credit to the side. They really improved and the quality of play today was immense. The way they raised themselves this afternoon was fantastic."Reuse content