Ian Caffell's men, who occupied bottom spot in the division for much of the season, made 215 batting first against their Berkshire rivals.
And they then bowled Theale & Tilehurst out for 146 to move safely clear of the bottom two places.
Wokingham CC strengthened their grip on second spot in Division One with a 69-run win over Henley 2nds.
The runners-up position is now the best Wokingham can hope for after Reading wrapped up the title against Finchampstead at Sonning Lane.
Dan Reddyhough's men look favourites to finish second with just one game of the season remaining after making 189-9 against Henley.
Stevie Smidt (52) and Reddyhough (51) both made half-centuries and the bowlers then dismissed Henley for 120.
Finchampstead could still finish in the top half of the table following their draw against Reading.
Departing Reading skipper David Barr top scored with 77 as the home side made 221-8 batting first.
Finchampstead denied Barr victory in his final match at Sonning Lane as they closed on 179-7.
Eversley are set to miss out on the Division 2a title despite easing past Cookham Dean by nine wickets.
With leaders Datchet also winning, Eversley are 20 points off the pace heading into the final weekend.
Royal Ascot beat Henley 3rds by eight wickets in Division 3a with Kevin May taking 6-56 and Nick Sweetman hitting an unbeaten 57.
* SEE THURSDAY'S NEWS FOR REPORTS AND REACTION.