O'Halloran had three months at Wycombe and since has been capped at full level by the Republic of Ireland, despite not having yet broken into Villa's first team.
"He's signed the extension to his contract, now he wants to play," said O'Neill.
O'Neill's decision could now interest Wolves and Ipswich, who are known to have O'Halloran on their radar.
"There's a number of teams interested in some of our players and clubs have been asking about him.
"That was some time ago and we might have to resurrect the interest because at the time I wasn't interested in doing anything.
"I'll think about Stephen. It was a great experience going to Wycombe - he ended up playing in the semi-final of the League Cup, which he would never have dreamed about."