How do I insert a record into a table?

I want to write a query like:

INSERT INTO table SELECT func(args);

where func is defined as:

CREATE OR REPLACE FUNCTION func(args)
RETURNS table
AS $_$
    ...
$_$ LANGUAGE plpgsql;

Unfortunately, when I try to do this, I get:

ERROR: column "first_column" is of type integer but expression is of
type record

I get this error even if I list the columns:
INSTER INTO table(first_column, second_column, ...) ....

So how do I take a record returned from a function, and insert it as a
row into a table?

Brian