help understanding "no" after dictionary form of verb

I'm pretty new to Japanese.

I'm working my way through a children's book, もり の なか, a translation of In the Forest.

I'm working on this sentence:

けれども、ぼくを みると、 あそぶのを やめて さ けびました。

In the original, it's the second half of

"Two little monkeys high up in the trees
Stopped playing and shouted when they saw me."

Click to expand...

I'm trying to understand the の in あそびのを .

It seems like it's turning the dictionary form of "play", あそぶ, into a noun, maybe? I tend to think of the を particle being attached to nouns.

I tried turning to Japanese the Manga Way and Japanese Verbs and Essentials of Grammar for help; I didn't find anything in the latter, but I found some info on what JtMW calls the "explanatory の", which seems to add emphasis or suggest explanation.

Can anyone help me understand what the の means and why it's there?

Thank you!

That's not "explanatory の" but a nominalizer. It's used to change a verb into a noun(to nominalize), as you inferred, just like the gerund "playing" for a verb "to play" in English.

Thank you, Toritoribe, that's most helpful!

ありがとうございます！