Doak had a bogey-free day to lead at 6 under at the Real Club de Golf de Sevilla.
Montgomery was tied with fellow Scot Steven OHara, Jean-Francois Lucquin of France and Juan Parron of Spain, with six others another shot back.
Thats three tournaments in a row with a 67. Things are looking up, said Montgomerie, who is looking for his 32nd tour victory. It was a very nostalgic round. I was thinking about all sorts of things ' my three PGA wins, eight Order of Merits and being Ryder Cup captain.
Ive thought about that every minute of every day since I was appointed.
Montgomerie, who is captaining Europe against the United States at next years Ryder Cup, had four birdies over his first six holes after starting on the back side.
The 45-year-old Scott then bogeyed the 16th after landing in the water, but recovered by sinking back-to-back birdie putts on the 18th and first to get to 5-under. Montgomerie, who credited a switch to a belly putter for his improved putting, holed from nearly 20 feet for another birdie at the fifth after a bogey at the previous hole.
People say that being Ryder Cup captain will hurt my game, but I think exactly the opposite. Ive been looking for ways to relax on the course and I think Ive found it, said Montgomerie, who has 182 top-10 finishes but none since last Junes French Open. He has slipped to 137th in the world rankings, which will keep him from qualifying for next months Masters.
I have to try and get back in the top 50, thats the goal for the season. If I can do that, gain 80 spots in a year, that will be a very good effort, Montgomerie said.
Five shots separated the first 51 players in the 156-strong field, with two local favorites in danger of missing the cut at the $1.35 million event. Course designer Jose Maria Olazabal and host Juan Angel Jimenez were both tied for 88th at 2 over.