Both are approaching the end of the second year of their scholarships, with O’Neill making his first-team debut as a substitute against Queens Park Rangers last Saturday.
Bennett, 18, who is a real talent, had returned to action in the last couple of months after recovering from a serious knee injury which required surgery.
The duo were both in the Under-19s side which beat Port Vale 8-1 on Tuesday to clinch the North West Youth Alliance title.
The extensions of their current contracts are something of a safety net and allow them to play in both the first-team and youth team next season, with them getting the offer of professional terms on top of that.
North End manager Ryan Lowe said: “For Mikey, the minute I came in and saw him, he was scoring goals for the youth team, so we were quick to get him up to the first-team and he’s shown that he can handle it.
“I’m really pleased that we’ve taken the extension and I’ve said to him today that’s the easy part, now the hard part is getting around the squad, getting in the team and making more appearances.
“I’m really looking forward to working with him, especially in pre-season, because I think he’s got a really good chance of making a career for himself and hopefully it’s at Preston North End.
“With Aaron, we felt we had a duty of care to him because he’d been out injured for 10 months, but I’ve heard the reviews from Nick Harrison, the academy staff and Paul Gallagher.
“He’s been scoring goals as an attacking eight, and we felt it was only right that we gave him the extra year to take a good look at him in pre-season.
“Training with the first team is obviously a lot harder than it is with the academy, so it’s a challenge for him now to get super fit, come back in pre-season firing on all cylinders and again he’s another youngster coming through the ranks who we want to give chances to.”