Grosjean's position at the Lotus team has been far from secure since joining on a full-time basis at the start of 2012, with a series of early-race incidents tarnishing his reputation and even leading to a one-race ban last season.
This season the Frenchman has more than repaid his team's faith with a string of strong performances in the second half of the campaign, regularly out-qualifying world champion team-mate Kimi Raikkonen, who is quitting to move to Ferrari next season.
Grosjean's upturn has come at exactly the right time, with his third-placed finishes in Korea and then Japan last time out a timely reminder to Bouiller of his undoubted talent.
Grosjean's past transgressions have left Lotus reluctant to take up their option on him for next season until now, but speaking after Friday's practice sessions for this weekend's Indian Grand Prix, Bouiller heaped praise on the ever-improving 27-year-old.
"We are definitely pleased with his performance, since Germany actually," said Boullier.
"Clearly, something switched on and he is working better. We are pleased that he is stepping up. We don't have a policy of driver number one and number two but we needed him obviously to step up, yes.
"Romain has a contract signed anyway for next year. It's just, say, a matter of confirmation. We are being prudent after last [season] obviously. But I think it's on its way to be confirmed soon."
The identity of the occupant of the second Lotus seat from 2014 is less clear, although current Sauber driver Nico Hulkenberg is widely regarded as the front-runner, although Williams' Pastor Maldonado is also under consideration.
Felipe Massa, ousted at Ferrari by Raikkonen's return, is also in the picture, but it appears Lotus test driver and 2012 GP2 champion Davide Valsecchi is a rank outsider, with Bouiller keen to have some experience in both cockpits next season.
"Davide is on the list but to bring to the grid next year a driver with no experience is a huge step for them - I've done it twice with them, first with [Vitaly] Petrov and then with a semi-rookie in Grosjean and I think I've had enough to be honest with you," he said.
"Davide is on the list because we consider him as a good driver, as a GP2 champion, but it's true that if you favour a scenario for next year it will be a driver with experience.
"If we cannot find any driver with experience, fitting the strategy of the team, obviously we will go for a rookie driver and then Davide is obviously on the top of the list. It looks harsh, I'm sorry but it's true."
Asked when the identity of Raikkonen's replacement would be known, Bouillier replied: "Hopefully a few days."