"congregate with" is correct and usable in written English.
You can use it to refer to a group of people gathering together. For example, "The students congregated with each other before class."
Now, with cellphones, protesters can congregate with only minutes' notice.
Populations move considerable distances between seasons, and throughout the year individuals often congregate with birds of the same gender.
A fruit stand offers discounted strawberries, near a baseball diamond where geese congregate with pigeons in left field.
They know how to move independently toward the light, avoid obstacles, claim territory and congregate with other similar creatures.
It's no longer only solely about creating a group of fun, nice people to congregate with; it's now more strategic.
People congregate with friends or alone on their boats on the lakes, or unwind at home along the waterfront.
Bands of Christian youths congregated with sticks and iron bars, promising to defend their neighborhoods.
For the Nafion membranes, the active proton paths became denser and congregated with each other at over 60% RH, resulting in the formation of well-connected networks.
To avoid its spread, farmers in the quarantine area have been told to keep people off their property and to avoid congregating with other farmers.
In downtown Brooklyn, DeSouza and hundreds of other Packer students congregated with more than a thousand other students mostly from nearby private schools in front of Borough Hall.
A handsome driver collected us from the airport in his Mercedes-Benz, and the group congregated with a glass of champagne in the lobby of the Boscolo Exedra, our five-star hotel at the Piazza della Repubblica.
