A point from their final group game against Antrim on Wednesday evening will be enough to keep Mickey Harte’s side on course for a fourth successive title.
Patrick Quinn’s 43rd minute goal finally broke the spirit of the Ranch lads, moments after Jerome Johnston had missed a chance to bring his side level with a penalty, which was saved by Mickey O’Neill.
Connor McAliskey marked his first appearance of the season with three early points as the Red Hands rolled into a 0-5 to 0-1 lead.
But after a bright start, they failed to score in the final 18 minutes of the first half, with Emmet Bradley narrowing the gap to three.
But St Mary’s were reduced to 14 men with the dismissal of James Morgan. Trailing by 0-5 to 0-2, they were on the defensive almost throughout the second half. St Mary’s did have a chance to go level when they were awarded a penalty, but Johnston’s kick was superbly saved by O’Neill.
The Red Hands responded instantly with a palmed goal from Quinn for a six-point advantage.
The depleted visitors had little resistance left, and substitutes Sean Cavanagh, Kyle Coney and Peter Hughes all landed points, along with new boys Rory Brennan and Cathal McShane.
Scorers for Tyrone: P Quinn 1-1, C McAliskey 0-3, S Cavanagh 0-2 (2f), R Brennan, C Cavanagh, P Hughes, C McShane, K Coney (f), P Harte 0-1 each.
Scorers for St Mary’s: R Johnston, E Bradley, B O’Hagan (f) 0-1 each.
TYRONE: M O’Neill, A McCrory, R McNamee, C McCarron, R Brennan, D Quinn, P Harte, C Cavanagh, P McNulty, M Donnelly, C McShane, P Kane, P Quinn, C McAliskey, S McGuigan.
Subs: T McCann for McCarron (14), S Cavanagh for McGuigan (47), P Hughes for Donnelly (49), J McMahon for McNulty (60), K Coney for Quinn (60), B Tierney for McCrory (65)
ST MARY’S: J Deeney, A Beattie, B Og McGilligan, C McCooey, J Morgan, A Forker, H Loughran, C McCann, E Bradley, P McBride, K McGeary, T Canavan, B O’Hagan, J Johnston, R Johnston.
Subs: T McCaffrey for Canavan (56), R Wilson for Beattie (63), A Nugent for McBride (65).
Referee: R Barry (Down).