yield return multiple IEnumerables

Question

I have a test function that returns an IEnumerable, which inside, I want to yield return other functions that return IEnumerable.

public IEnumerable Foo()
{
    Console.WriteLine("Foo!");
    yield break;
}

public IEnumerable Bar()
{
    Console.WriteLine("Bar!");
    yield break;
}

public IEnumerable Foobar()
{
    foreach (var o in Foo())
    {
        yield return o;
    }

    foreach (var o in Bar())
    {
        yield return o;
    }
}

However, this "Foobar" function will have many more inner functions that return IEnumerable.

Is there any shorter way to do this instead of having to foreach and iterate over very function?