Dunstable’s first team will be playing Saracens Herts League Championship cricket next season following a nail-biting Division One win over Knebworth at the weekend.
Guy Hill and Jack Kilduff took three wickets apiece as they bowled their visitors out for just 150.
In reply, Dunstable were cruising at 74-2, with 42 from Hill, before collapsing to 132-9, as captain Brad Matthews was out for 30.
However, Mike Alston and Mark Rochester guided them to 155-9, sealing promotion, just two points ahead of third placed Kings Langley.
The IIs finished their season with a narrow victory over bottom side Hertingfordbury.
Dunstable batted first and scored 247-5 as Ian Horton made an unbeaten hundred coupled with 75 from Lee Pratt and 33 for Ian Gilbert.
This proved just too much for the hosts as they were all out for just 242, Raz Khan returning figures of 5-51 to ensure a sixth place finish in Division 4B.
The IIIs suffered a disappointing two-wicket defeat against Pirton to end their season. Dunstable set Pirton 189 to win after being bowled out for 188 with Adam Lewis making 57 and Shoaib Rashid top scoring with 68.
Pirton lost eight wickets in reply as they chased their target inside 40 overs, ensuring Dunstable finished fourth in the league.
The fourth team weren’t in action this week, however a loss for Kempston Methodists means that Dunstable stayed up in Beds Invitational League Division One.