Goosen shot a 69 Friday to bring his total score to 11-under-par 131.
He leads young Australian Adam Scott (68) by two shots, and Paul McGinley (67), Thomas Bjorn (67) and Barry Lane (65) by four.
Under continued rainy weather in Glasgow, Goosen appeared to pick up right where he left off early Friday, as the winner of this years U.S. Open grabbed two birdies in his opening four holes, and then birdied the par-4 16th (his seventh of the day) to ultimately go out in 3-under 32.
However, while he torched the front nine in 30 on Day One, the 32-year-old could do no better than 1-over-37 Friday.
As a result, his overnight lead narrowed from three shots to two entering the weekend, and brought a host of talented players into the mix.
In outright second, Scott might be the most talented of them all.
Following his season-opening win at the Alfred Dunhill Championship, Scott was quiet for several months, but has resurfaced as of late, with a third-place showing in Junes English Open, and a sixth at the Irish Open earlier this month.
Friday, the 22-year-old was even-par for his round through 15 holes, but birdied his final three holes of the day for 68.
Bjorn, too, is looking for his second win of the year, after defeating Tiger Woods earlier in the season at the Dubai Desert Classic.
The tall Danes round Friday consisted of six birdies and two bogies.
At 6-under-par resides another interesting group of players, as John Daly (68), Tom Lehman (66), Darren Clarke (67) and Greg Chalmers (66) all find themselves just five back entering the weekend.
While Clarke is coming off his first win of the year at last weeks European Open, Daly is looking for his first professional victory since the 1995 British Open.
Like Daly, Lehman has been relatively quiet since his triumph at the 96 Open ' he has only won twice on the American PGA Tour.
With a return of good play, the Minnesota native should be licking his chops, as next weeks championship returns to the site of his only major victory at Royal Lytham and St. Annes.
Full-field scores from the Scottish Open at Loch Lomond