The race saw Collard collect his first podium of the season with a third place, while Foster flew off the circuit at high speed and the car launched itself over the tyre wall.
Luckily Odiham’s Foster was unhurt and his car was rebuilt in time for race three.
Foster was bemused by the incident, which involved Rob Austin, and said: “Church is a 140mph corner and the fastest one in the championship. It is not somewhere you go around hitting other cars as Rob Austin did.
“It was blatantly stupid and I was lucky that the car spun round a couple of times, taking some speed out before I ended up in the bushes.”
Foster said: “The clerk of the course thought it was an outrageous move and he was excluded from the race two result.”
Meanwhile, at the front of the pack, Collard was bringing his ebay Motors BMW home in third place for his first podium finish of the season.
Collard said: “It was a great result as Thruxton is not the best circuit for the BMWs.”
The Hook driver had a good weekend as he qualified the top BMW in eighth place and in race one finished fifth.
In race two he got a great start and challenged leader Andrew Jordan in the opening lap before taking his third place.
In the reverse grid final race, Collard started from eighth and was in the top five until he came under attack from the Hondas of Gordon Snedden and Matt Neal.
Shedden touched Collard as they came into the chicane and forced the Hook driver to miss the chicane completely to avoid a crash. The Scottish driver is under investigation for the move.
Later, Collard had a coming together with Matt Neal, which forced both onto the grass, and he eventually finished 10th.
Collard said: “The Hondas decided it was a stock car race and it was completely out of order.”
For Odiham’s Foster, the meeting saw him qualify 15th, which is where he finished race one, and then in his last race he started 27th and finished 20th.
Foster said: “To be honest Thruxton is not my best circuit, but I was happy with qualifying and in the first race we held our own.
“In the last race there was a few issues with the car, but after the crash in race two this was to be expected.”
Rob Collard’s son Ricky was also in action in the Formula Ford Championship and left his home track in second place in the Scholarship Class after he returned a ninth and two eighth-place finishes.
He lacked some pace during the weekend, which his team Falcon Motorsport will look to put right ahead of the next round.
In the Ginetta Junior Championship, also at Thruxton, Jack Rawles, backed by Basingstoke Skip Hire, enjoyed a fifth place in race one after he fought his way back after an early spin with Ryan Hadfield.
In race two, he looked set for seventh until he was turned around at the chicane on the final lap by Pedro Cardoso and ended up 12th.
The championship now moves on to Oulton Park in Cheshire, with the next races on Sunday, June 8.
The week before Thruxton, Rob Collard’s youngest son, Jordan, was in action in the opening round of the British Karting Championship and finished 15th after being spun round early in the race.
The next round of the championship is in a fortnight’s time at Buckmore Park, in Kent.