Getting an asset Url from an entry loop into a meta tag
I didn't have a full understanding of how blocks work, but I've solved my problem. I think because I was trying to set the variable in my template outside of the block (and I was trying to bring it into my _layout.twig file without referencing the block I was calling) nothing was getting properly passed from one file to the other. The solution I'm now using looks like this:
_layout.twig:
&lt;meta property=&quot;og:image&quot; content=&quot;{% block ogImage %}{% endblock %}&quot; /&gt;

template.twig:
{% block ogImage %}
    {% for image in entry.eventImage.all() %}
        {{ image.url() }}
    {% endfor %}
{% endblock %}