Giroud was heavily criticized following Arsenal's 3-1 defeat to Monaco in the opening leg of their UEFA Champions League last-16 tie last week.
The France international striker has responded with goals in consecutive Premier League fixtures.
Giroud scored the opener as Arsenal accounted for Everton 2-0 on Sunday, while the 28-year-old netted the first of his side's two goals against QPR on Wednesday.
"Olivier has that mental strength, he's strong mentally too," Wenger said. "He can take criticism and respond, and he's shown that.
"I feel that was a bit harsh on him because he missed some chances but that can happen. We were all down after the Monaco game, but we responded well against Everton, and the confidence we got against Everton paid off tonight."
Giroud has scored 10 Premier League goals for Arsenal this season, three less than teammate Alexis Sanchez (13).