McCormack, the subject of "two or three" rejected bids from Sky Bet Championship rivals Middlesbrough, ran on to Luke Varney's chest down, skipped round Kamil Zayatte after wrong-footing the former Hull defender and steered home a low shot beneath visiting goalkeeper Chris Kirkland early in the second half.
It was a fine solo effort from the 26-year-old, omitted from Gordon Strachan's Scotland squad for the midweek defeat to England at Wembley, and cancelled out Wednesday's first-half opener from summer signing Zayatte, who headed home his first goal for the club.
The transfer window closes on September 1, but although McDermott has made his feelings plain, the continued silence from Leeds' owners GFH Capital on McCormack's future could offer Middlesbrough, or any other rival clubs, enough encouragement to make a further improved offer.
"I want him to score those goals in August, July, September, any time because that's what football's all about - that bit of quality," McDermott said.
"I said to the lads at half-time, let's not wait for anything, let's grab it, someone grab it and he certainly did that.
"It was a fabulous goal. We've turned down two or three bids and you know my view, that's not changed.
"I've spoken to Ross and you saw the quality that he brings.
"You saw his celebration as well. He loves this football club and I like working with him."
When asked whether Middlesbrough were wasting their time putting in another bid, McDermott added: "That's up to them, they can do what they like.
"As far as I'm concerned, Ross wants to be here, I want him to be here, that's their prerogative to do what they like."
McDermott said the aim was to win all their home games this season, but he was satisfied with both his side's performances and points return from their first three matches.
"The players have given me everything and the crowd appreciate that," McDermott said. "They stayed with us again today and they see that we're trying to find a way to get results.
"We want to win at home, but that's five points from three games and we look forward to the next one."
Wednesday were good value for their point, their first of the season following successive defeats to QPR, Rotherham in the Capital One Cup, and Burnley.
Owls winger Michail Antonio forced Leeds goalkeeper Paddy Kenny into two crucial saves in the closing stages when both sides chased the winner.
"We played well and I think most managers would have taken a point from Elland Road before the game," said manager Dave Jones.
"But I thought we should have taken all three points. We had the chances, we might have had a penalty and in the end we were unlucky.
"We should have done better for their goal and we will continue to work on those situations. But overall we have done ok, we are off the mark and now we move on to the next game."
Owls right-back Lewis Buxton made an impressive first appearance of the season following shin splints and Jones added: "Lewis was absolutely magnificent.
"He came into the team today on the back of three days training and you wouldn't have thought he had been away."
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- Kamil Zayatte