Treeton made 162-9 with opener Steve Foster top scoring with 51 and Simon Guy hitting 38.
Tight bowling from Pete Wilson, 4-32 and Jason Meadows, 3-36, prevented Treeton getting away later on.
Openers Tim Farmer and Matt Thewlis fell cheaply in Elsecar's reply but 50 from Brett Hunsley held things together and the last over arrived with five needed.
Three were still needed off three balls but then spinner Dave Burden bowled a wide and a no ball before Matt Danks struck the winning boundary off the next ball to leave Elsecar 163-7.
n In the league, Premier Division leaders Wickersley enjoyed a crushing win over Shiregreen, and if they can avoid defeat in their September 10 match against Elsecar, look odds-on to be champions again.
Richard Harrison's 47 not out was top score in their 226-9 and Shiregreen were rushed out for 87 Imran Adrees bagging 5-27. Second placed Whitley Hall provided all-rounder of the day in Jaco Castle who slammed a fiery 109 of the Ecclesfield Club's 308-7, then claimed 7-55 to hold Oughtibridge to 203-9.
Elsecar made 225-8 with opener Tim Farmer striking 75 and captain Lesroy Weekes 58 before sending back Phoenix for 199 and Treeton were Premiership high scorers, reaching 317 thanks to a glorious 163 from Simon Guy, at Aston Hall, who hung on at 184-9.
Matt Burrows hit 73 as Wath totalled 247-5, too many for Norton Oakes who closed on 195-8 with Mahmood Hamid hammering 94 and Collegiate had the edge over Doncaster Town, Mike Simpson hitting 78 and Joe Root 55 of their 238-7, Town finishing on 188-9, Ashley Fidler 54. Riaz Richards included a hat-trick in his 4-46.
Rockingham went top of Division One after their win at Hallam, while Darfield included two century makers against Dodworth, Richard Heaney cracking 153 and Andy Townsley 100 not out.
Stuart Coleman blasted 167 of Tickhill's 226-6, but was on the losing side as Warmsworth hit back with 227-4, Australian Mick Kenny unbeaten on 103.