SEA ISLAND, November 10, 2013 (AFP) - Kirk holed a 24-foot putt to complete a two-under-par 68.
Baird followed with an eight-foot birdie putt for a 67.
Their 54-hole total of 10-under-par 200 left them one stroke in front of Kevin Stadler, Brian Gay and Australian John Senden going into the final round.
Sunday promised to be a shoot-out, with the top 12 players separated by just four strokes.
"It's not like you can just go out there and play conservative and try to hold onto your lead," Kirk said. "It's sort of anybody's game.
"Obviously, I'm happy to be tied for the lead right now because that's one less shot that I've got to go get tomorrow. But I've got to go play a really good round tomorrow, and hope that nobody plays a really great round tomorrow."
Brendon Todd and Scott Brown shared sixth place on 202, while Jason Kokrak was alone on 203.
Four players were tied on 204: 2012 US Open champion Webb Simpson, Matt Kuchar, Daniel Summerhays and Matt Every.
Baird is in search of his first US PGA Tour win in his 365th start.
The 41-year-old had surgery on both shoulders in 2012 and missed all of the 2013 campaign. He is hoping that renewed good health will help him find that elusive tour title in the new-look 2013-14 season that features six events before New Year's.
After following two early birdies with back-to-back bogeys at the ninth and 10th, Baird closed his round with three birdies in a row at 16, 17 and 18.
"It's a great way to finish and it puts me in a better position going into tomorrow than if I'd have just finished with pars," Baird said. "That would have made the work tomorrow considerably harder."
Kirk rebounded from bogeys at six and 12 -- both par threes -- with birdies at 13, 14 and 15 before punctuating his round with his birdie at the last.
Stadler took advantage of benign conditions to climb up the leaderboard with a five-under 65 that included seven birdies and two bogeys.
Gay had five birdies and a bogey in his 66 and Senden posted a 68.
Leading third-round scores on Saturday in the US PGA Tour $5.5 million McGladrey Classic (USA unless noted, par-70):
200 - Chris Kirk 66-66-68, Briny Baird 63-70-67
201 - Kevin Stadler 68-68-65, Brian Gay 63-72-66, John Senden (AUS) 66-67-68
202 - Brendon Todd 68-67-67, Scott Brown 66-68-68
203 - Jason Kokrak 69-65-69
204 - Matt Kuchar 68-68-68, Daniel Summerhays 69-66-69, Matt Every 67-68-69, Webb Simpson 65-68-71
205 - Charles Howell 69-70-66, Scott Langley 66-71-68, Brian Harman 67-68-70, Tim Clark (RSA) 67-67-71
206 - Robert Garrigus 65-74-67, Zach Johnson 70-68-68, Brice Garnett 67-72-67, George McNeill 62-76-68, Ted Potter 67-67-72
207 - Cameron Tringale 70-69-68, Charley Hoffman 66-73-68, Heath Slocum 67-71-69, Robert Karlsson (SWE) 68-68-71, Will Claxton 65-71-71, John Rollins 65-76-66, Jonathan Byrd 66-69-72, Kevin Chappell 65-68-74