Sarvesh Shirasat took Osterley to within three games of a dream final at Lord's on Sunday.
All-rounder Shirasat took 4-35 and hit an unbeaten 61 as Osterley beat East Molesey by five wickets in the ECB Cockspur Cup.
They now face Oxford in the regional final on July 6, where victory would put them into the national quarter-finals, and bring that Lord's date one step closer.
Aman Butar (3-24) and Fazal Ahmad (2-10) also returned good bowling figures as Osterley bowled out Molesey for 148, before Ahmad smashed 57 as they made 150-5 for victory.
The previous day, Osterley thrashed Turnham Green by 147 runs in the Middlesex Championship, Division One.