The Pears were bowled out for 206, losing their final five wickets for 53 this morning, with James Tomlinson finishing with three for 52.
Leaders Northamptonshire are on course for a second win in three with Gloucestershire 111 for four in their second innings - 101 runs behind.
Australia seamer Trent Copeland grabbed two of the wickets to fall, for the cost of 22 runs.
Lancashire's rain-affected contest with Kent continued to progress at a crawl at Old Trafford.
Lancashire were 120 for three, with Karl Brown unbeaten on 48, in reply to 244.