The Hungarian has been sidelined since suffering an anterior cruciate ligament injury against Queens Park Rangers in January.
But he played for an hour as the Baggies' U21s went down 1-0 against Arsenal, and was thrilled to get back on the pitch.
"I ran onto the pitch with great excitement because I had the chance to play again after a long time," Gera wrote on his own Facebook page.
"It's true it was just an Under-21 game but at the moment this is a great forward step for me.
"In the first five to 10 minutes I was short of breath but then I could get used to the speed of the game and felt I would be able to run until the following morning.
"Originally I was to play 45 minutes but in the break I begged for another 15 minutes. Today (Friday) I do my regeneration on a bike."