"Almost every Saturday, for about six and a-half years, we get an average of 32 parkrunners and walkers," organiser Rod Deverson said.
"We never cancel no matter the weather, so no matter how frequently or randomly you want to come, you know we’ll always be here and it doesn’t cost anything."
Parkrun is a sponsored global phenomenon which started in Bushy Park, London in 2007.
There are now about 3000 official parkruns around the world. Run data is managed by a volunteer team, and there is a defibrillator on hand to ensure participants' safety.
Organisers ensure nobody is left behind.
"My husband John didn’t like running at all until he started walking the parkrun," Ann Douglas, who has attended runs from the beginning, said.
"Now he runs his 5km here and goes out a couple of times a week early in the morning for five kilometres of his own.
"We find as we get older this is a good way to meet other people. It’s very social."
Saturday’s 300th run brought participants from Mosgiel and Upper Hutt. Some participants had clocked up to 250 parkruns, and some Saturdays drew overseas participants who had found the local group online.
"We’ve had more than 1200 different people finish the run over the years," Mr Deverson said.
"That’s 9830 finishers all up. The fastest time for our 5km is 16min24sec but the average finish time is 40 minutes and one second.
"Slow is good because parkrun’s bottom line is to invite and include runners and walkers of all ages and abilities...
"Some people have this as their only run; others fit it in with another training programme of their own because it’s standardised and you can monitor and challenge yourself with it if you do like to be competitive, even just in your own mind," he said.
"Some people are quite proud how it’s a bit of a tribe or a bit of an addiction, but it’s really just that with parkrun anybody can join at 9 o’clock every Saturday morning."
