The new Polaris World Aprilia rider was on top after 10 minutes of the half hour session, before being replaced by Rafaele de Rosa during the middle stages.
Smith then fought back with nine minutes to go, retaking the top spot by 0.151secs - before pulling a massive 0.810secs clear of the field on his very next lap, aided by a tow from some slower rivals.
But just minutes later and Smith was walking gingerly through the floodlit Losail gravel after an unseen fall, meaning his provisional pole would be left unprotected during the vital closing stages.
Ultimately Bradley's 2min 5.086secs lap proved enough to hold off fellow Brit Danny Webb by 0.3secs at the chequered flag, as the UK enjoyed a dream start to the new season.
"Apart from the crash it was a really good session although this is just the first qualifying and it's the race that counts," explained Smith. "I think we can go faster tomorrow."
"It's great for British fans although I didn't think my lap was that fast and I was surprised when P2 came up," added Webb.
Mike di Meglio and Simone Corsi completed the provisional front row, while reigning world champion Gabor Talmacsi had to be content with seventh. Team-mate Sergio Gadea faired far worse, being left in last place after being hit by his factory Aprilia during an early fall.
British rookie Scott Redding, an excellent third in free practice, finished his first qualifying session in a solid eleventh.
First qualifying - Qatar:
1. Smith (Aprilia)
2. Webb (Aprilia) +0.307secs
3. di Meglio (Derbi) +0.504secs
4. Corsi (Aprilia) +0.810secs
5. de Rosa (KTM) +0.923secs
6. Cortese (Aprilia) +0.932secs
7. Talmacsi (Aprilia) +0.976secs
8. Terol (Aprilia) +1.327secs
9. Bianco (Aprilia) +1.416secs
10. Vasquez (Aprilia) +1.423secs
11. Redding (Aprilia) +1.524secs
