As interior ministers from the European Union members states held their emergency meeting, volunteers at the camp across on the road from the city's main immigration office said its population had grown to around 1,000 over the weekend.
Most are exhausted Syrians, Iraqis, Afghans and Somalis seeking food and shelter. They have arrived over the past two weeks, only to find that the government-run shelter near the Brussels immigration office is open only at night, has no showers and is equipped for just 500 people or so.
"It's a shock to have to live in the park but it is nothing compared to what I've been through," said Mohib, a 28-year-old computer engineer from northern Syria, showing the scar of a wound sustained in a rocket attack in Aleppo.
"I can wait five years if I have to. Europe needs to realise we are not going back to that hell," said Mohib, who like many others declined to give his surname, still wary of reprisals.
The ministers are set to agree to relocate 120,000 more asylum-seekers around the EU, according to draft conclusions of Monday's meeting. But after fierce opposition to compulsory national quotas, particularly from east Europe, a decision on who should accommodate them would be left till later.
Germany and Sweden are the favoured destinations for those escaping conflict and poverty in the Middle East, Asia and Africa. But many people in the park said they were now trying Belgium in the hope there was more chance of gaining asylum, particularly for victims of the Syrian civil war.
Some Syrians accused migrants from elsewhere of pretending to be from the country to improve their chances of asylum.
"Everyone is saying they are Syrian in Germany now, there's not enough space for us who are genuine refugees," said Yamin, 22, who said he fought for rebels against President Bashar al-Assad and then fled to Turkey. He spent 11 days crossing through Greece, paying $1,200 to people smugglers, to reach Belgium five days ago.
In the shadow of the gleaming office blocks in central Brussels, the park is run by volunteers who took to Facebook to channel the generosity of local residents into orderly donations of tents, food, clothes and children's toys.
Belgium's state agency for asylum said last week it had more donations of clothes than it could handle and would more than double the number of accommodation places available across the country to 36,000.
A hand-written sign in French on one of the wire entrances to the Brussels park also tells would-be givers of charity that, for the moment at least, there is no need for more donations. Other signs remind people that the migrants need care.
"Imagine if it was you," read one banner.
"Two weeks ago, the number of people waiting at the immigration office became unbearable. It was completely chaotic," said Elodie Francart, a part-time aid worker who has taken time off from her teaching job to help organise the camp. "We came to help and the response has been tremendous."
Migrants are given three meals a day, medical care, a chance to shower and some time to relax, play football or listen to music and shows put on by volunteers.
That has drawn criticism from some local people and politicians that the camp is too attractive and is serving as a magnet for new arrivals.
Belgium's state secretary for asylum and migration, Theo Francken, caused a stir this month when he tweeted that the camp "was apparently more comfortable" than the federal asylum centre run by the Red Cross.
But now the camp is close to bursting as new arrivals come every day and progress at the immigration office is slow. On Monday morning, crowds of people waving papers, some with children on their shoulders, tried to attend appointments for fingerprinting to lodge their asylum request.
Rumours of police evacuation of the park any day haunt many in the camp.
"What's next? People are tired, politicians hardly come and the weather is turning wetter and colder," said camp organiser Francart in her marquee headquarters where a white board shows a hand-written weather forecast for the week ahead.
"We desperately need a better response," she said, stepping her way through the blue and red tents to a meeting.