PRAGUE, August 23, 2014 (AFP) - That put him two clear of Denmark's Soren Kjeldsen and Donaldson who still remains on course for a Ryder Cup spot.
"It wasn't my best ball striking round but it was a good scoring round, that's for sure," said Dredge, who was runner-up in Denmark last weekend.
"I lost my card at the end of 2012 and had a few health problems to sort out.
"This year my category is quite low, so when I do play I've got to go out and play well. I'm sorting things out and hopefully it will soon be gone."
Donaldson, 38, had led after the first two rounds and went into Saturday's third day with a one-shot lead over France's Gregory Bourdy.
Dredge turned up the pressure on the closing holes with birdies on the 14th and 15th.
He missed an eight foot putt at the last which would have seen the two-time European Tour winner equal the course record.
But Donaldson then bogeyed the last to give his compatriot a two-shot lead as the 41-year-old seeks a first win since 2006.
Leading second round scores in the Czech Masters at the Albatross Golf Resort, Prague, on Saturday (GBR/IRL unless stated, par 72):
204 - Bradley Dredge 68 70 66
206 - Soren Kjeldsen (DEN) 68 70 68, Jamie Donaldson 66 69 71
207 - Gregory Bourdy (FRA) 69 67 71
208 - Merrick Bremner (RSA) 70 68 70, Stephen Gallacher 70 67 71
209 - Paul Waring 68 71 70, Garrick Porteous 70 67 72, David Lipsky (USA) 69 71
69
210 - Sam Walker 69 71 70, Steve Webster 70 72 68, Tommy Fleetwood 72 65 73,
Matthew Baldwin 72 71 67, Kenneth Ferrie 68 71 71, Rikard Karlberg (SWE) 70 72
68, James Morrison 70 68 72
211 - Craig Lee 69 71 71, Mikael Lundberg (SWE) 67 76 68, Javier Colomo (ESP) 69
71 71, Peter Hedblom (SWE) 70 68 73, Shiv Shankar Prasad Chowrasia (IND) 68 75
68, Joachim B Hansen (DEN) 70 69 72, Andy Sullivan 69 73 69, Andrea Pavan (ITA)
72 70 69, Paul Lawrie 70 70 71
Selected:
213 - Haydn Porteous (RSA) 74 70 69
214 - Kim Sihwan (KOR) 74 67 73, Gaganjeet Bhullar (IND) 72 71 71
216 - Shiv Kapur (IND) 71 70 75, James Kingston (RSA) 76 68 72, Keith Horne (RSA)
217 - Hennie Otto (RSA) 70 71 76, Dylan Frittelli (RSA) 72 70 75
219 - Brandon Stone (RSA) 71 73 75