Ducati's Andrea Iannone remained on top during FP2 at Assen to complete a free practice double, narrowing fending off Valentino Rossi in the afternoon.
The rain stayed away and Iannone again set the pace on his Desmosedici GP16, lapping in 1m 35.591s to edge out Movistar Yamaha's Rossi by only 0.004s.
Italian Iannone, though, will have to start from the rear of the grid in Sunday's Dutch TT as a result of a penalty incurred after his collision with Jorge Lorenzo in Catalunya.
Rossi maintained his excellent form of late on the YZR-M1 as the 37-year-old targets his second successive win at Assen and his second MotoGP win on the trot following his victory in Barcelona last time out.
The Doctor had been lying in 11th place before storming through in the closing stages to throw down a challenge to Iannone.
Repsol Honda's Marc Marquez, who used a larger set of wings on his RC213V later in the session, slotted into third with a lap in 1m 33.724s as the championship leader climbed the order after languishing in 11th place in FP1.
Suzuki's Maverick Vinales impressed on the GSX-RR as he took fourth with a lap in 1m 33.892s, while reigning champion Jorge Lorenzo on the second of the Movistar Yamaha machines was fifth, four tenths down on Iannone and Rossi.
Ducati's Andrea Dovizioso and Danilo Petrucci on the Pramac machine were sixth and seventh respectively, while Aleix Espargaro completed the first eight (Ecstar Suzuki).
Spain's Pol Espargaro (Monster Tech 3 Yamaha) and British rider Scott Reddding (Pramac Ducati) were the top 10, while Dani Pedrosa will be aiming to improve on Saturday as he ended the day in 11th place after a lap in 1m 34.206s, which left him 0.615s off the top.
Avintia Ducati's Hector Barbera was 12th and one place ahead of Cal Crutchlow on the LCR Honda, who was followed by Bradley Smith (Monster Tech 3 Yamaha) and Ireland's Eugene Laverty (Aspar Ducati). Barbera came off at turn 3 but was able to walk away, while Crutchlow and Laverty also came off but escaped unhurt.
Aprilia rider Alvaro Bautista went down early in the session at turn 3 and was involved in another spill later in FP2, this time at turn 5. The Spaniard eventually finished 20th.