James McFadden had the final say with a 25-yard free-kick into the top corner which earned the home side a well-deserved Clydesdale Bank Premier League point in the 85th minute.
Michael Higdon had headed Motherwell in front with his 23rd goal of the season before Conor Newton levelled with a long-range strike into the top corner.
Motherwell came close on numerous occasions in the second half but St Mirren never lost their attacking ambition and substitute Lewis Guy finished off a neat move with 15 minutes left.
However, McFadden finished off the scoring to leave Motherwell three points clear in second place and with an eight-point cushion in the race for a Europa League spot.
McCall said: "I would say the same even if we lost - I was really proud of the players. I thought it was a terrific game of football on a really lively pitch, which was a bit dry and bumpy.
"I thought second half we were terrific. I thought first half we were dangerous and had opportunities. It was a cracking goal by them, having said that all four goals were well executed.
"But some of the stuff we played second half was terrific and I was really pleased with the performance against a good, good St Mirren side.
"(But) as good a team as St Mirren are, I think it would have been a travesty if we didn't at least get something out of the game."