Two home players, Angel Hidalgo, who carded a tournament-record eight-under 63, and Adrian Otaegui, share the lead with Australian Min Woo Lee on nine-under-par at the challenging Cadiz course.
But in-form Italian Open champion MacIntyre sits just four shots back in a tie for fifth after following his opening 67 with a 70, which contained four birdies in his opening six holes.
“Yeah, it was solid,” said the Oban man of his effort. “I just made a few mistakes late on there when I was trying to be too fancy and trying to create too much out of a shot rather than just sticking to the numbers’ game.
“But, as I said yesterday, under par around here is good and the way I was playing one-under probably isn’t a fair reflection, but I’ll take it.”
MacIntyre had moved to the top of the leaderboard early on at the Ryder Cup venue after mixing birdies at the 11th, 12th, 14th and 15th with a bogey at the 13th.
“I thought I was going to get nine holes with no wind as it’s normally nice and calm here in the morning, but it felt breezy after about five holes,” he added.
“I was making my score early on, I was getting going and it kind of stalled a little bit with my tee shot at 17, but there were lots of chances as it was soft.”
Malaga man Hidalgo swept through the field with a brilliant bogey-free round, which was one shot outside the course record set by Bernhard Langer in the 1994 Volvo Masters.
“It’s not (a place where you can be aggressive), not at all,” insisted MacIntyre as he looked ahead to trying to catch the leaders. “I feel I’ve got a lot of chances out there the way I play. Just now I’m driving it well and my iron play is the best it’s been in a long, long time.
“It’s just about getting that ball on the fairway and being aggressive off the tee and getting it as close to the green as you can without being blocked from certain angles.
“I’ve not played anything different today than yesterday. For me, it’s about playing smart but, once you are in position, you can be aggressive to the numbers you are trying to play to.
“It’s a golf course you can’t overpower - you just can’t hit a driver everywhere. You’ve got to plot your way round from A to B. It’s awkward, it’s difficult. It’s Valderrama - it doesn’t let up from the first tee shot to the last.”
Lee, the 2021 Scottish Open champion, lit up his 67 by making an eagle from three feet at the fourth while Otaegui signed for six birdies in his 66.
Marc Warren (73) sits joint-19th on one-under, with Richie Ramsay (74) making the cut on two-over and Stephen Gallacer (71) and Connor Syme (72) also progressing on three-over.
Defending champion Matt Fitzpatrick made an early exit on six-over after a second successive 74, but his younger brother, Alex, is through to the weekend on leve-par.