On the second day Barisal, chasing a commanding Khulna total of 269 in 80 overs, were bundled out for 104 thanks to Milton, Paltu and Zitu who shared nine wickets respectively.
Zitu was the most economical of the trio conceding 19 runs for his three wickets.
Moin with a responsible 43 and Tanveer (20), were the notable run-getters for the losers.
The win took Khulna into the three-day zonal final scheduled to begin at the same venue from May 10. The other finalists will be decided after Faridpur and BUET meet today.
In another zonal semifinal in Patuakhali, Pirojpur were in the driving seat against Narsingdi at the end of play on Day One.
Batting first, Pirojpur scored only 151 runs in 56.4 overs. Jashim top-scored with 36 while Mintu added 31 runs.
In reply, Narsingdi were tottering at 37 for five in 27 overs at stumps needing another 115 runs for victory.
Away in Bogra, Tangail moved into the zonal semifinals with a comfortable 54-run win over Natore.
Opting to bat first in a 50-over-a-side game, Tangail were all out for 227 in 49.5 overs with Shushanto hammering highest 71. Sughan (47), Rupu (24) and Islam (22) were the other contributors.
In reply, Natore managed for 173 in 47.3 overs.
In the two-day semifinal beginning on May 9, Tangail will meet Gaibandha.
In the day's other zonal matches in Dhaka, Gazipur beat Habiganj by 67 runs and Manikganj defeated Noakhali by five wickets to qualify for the next round.
Electing to bat first in a reduced 25-over match at the Dhanmondi Cricket Stadium, Gazipur scored 139 for nine with Iqbal notching highest 35. Besides, Evan and Jewel scored 30 runs each.
In reply, Habiganj were dismissed for 72 in 19.1 overs.
At the Dhaka Stadium, Manikganj, chasing a paltry Noakhali total of 77 in 25 overs, reached 79 in 24.4 overs with five wickets in hand.