The young midfielder was given a red card after a tussle in the penalty area saw Olsson hit the deck and tangle again with the 22-year-old, who then received his marching orders.
It looked like the Australian was just trying to free his foot from the grasp of his Swedish opponent but Phil Dowd gave a penalty in the belief he had stamped on the West Brom defender.
And McLeish was unhappy with the decision which he felt changed the game despite Chris Brunt firing the resulting penalty wide.
He said: “Having seen the pictures that I’ve seen it looks like he was extricating his foot out of Olsson’s grasp and it was quite significant for me that Olsson didn’t react to the alleged stamp.
“In those pictures that I’ve seen I feel aggrieved but maybe another picture will show us he did stamp on him.
“Going on what I’ve seen it looks like a poor decision, the referee hasn’t seen it, there was a little bit of a fracas between the two of them but Phil Dowd hasn’t seen that either and unfortunately we’ve had a man sent off.
“It really set us back because we had started well, Chris in fact had started extremely well as we tried to change the dynamic of the midfield.
“We were disappointed at the goals we lost, everyone was picking up their men this time but they were beaten in 50/50s and that’s what we have to improve on or it will be a long, tough season.”