Sussex defeated Yorkshire by an innings and 12 runs and Middlesex cruised to a 10-wicket victory over Nottinghamshire before lunch at Trent Bridge.
Durham beat Somerset by 48 runs at Chester-le-Street and they sit two points behind joint-leaders Sussex and Middlesex in the embryonic Championship table.
The writing had been on the wall for Yorkshire at Headingley after they were bowled out for 96 in the first innings and Sussex posted 356 in reply. They fared better second time round but they resumed day four on 228 for eight and could not last until lunchtime, despite the best efforts of Gary Ballance.
Sussex paceman Chris Jordan, who bagged six wickets in the first innings, took his eighth scalp of the match when he had Jack Brooks caught by Michael Yardy for five.
Ballance had moved from 46 to 63 when he was caught off Steve Magoffin, who finished the innings with five for 51, as Yorkshire were bowled out for 248.
Middlesex required 108 to win after Toby Roland-Jones struck with the first ball of the day, removing Andre Adams for 50, as Nottinghamshire were bowled out for 182.
Openers Chris Rogers (51) and Sam Robson (55) both hit unbeaten half-centuries as Middlesex cruised to victory.
Somerset resumed their second innings on 96 for two and with strong hopes of victory as they chased a target of 235. Craig Kieswetter hit 72 but once James Hildreth went for 27, Durham took eight wickets for just 90 runs.
Warwickshire are on course for a rain-affected draw with Derbyshire after 76 from Varun Chopra and Ian Westwood's 56 helped them to 201 for four in their first innings. Derbyshire posted 226.