Is "There was a group of people who were enjoying it" grammatically correct?

Solution 1:

If you want enjoying to apply to the group as a whole, you have to use that rather than who.

There was a group of people that was enjoying it.

When you use who, it refers to people, which is plural, so it needs a plural verb. Switching to that changes the reference to group, which is singular.

You can also say:

There was a group of people that were enjoying it.

There is a very subtle difference, I believe. The first emphasizes that the group as a whole is enjoying it. The second emphasizes that a number of people are enjoying it, and then defines the group in terms of those people.