Looking on the internet deeply has found these results:

AT THE GRAND OCCASION. is the most popular phrase on the web.

IN THE GRAND OCCASION. 149,200 results on the web	AT THE GRAND OCCASION. 1109,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
day politics. Today's meeting is a grand occasion. to Notional reserve for officials seconded in the interests of the service not included in the grand total. As MEPs, we have been confronted on several occasions recently with the problem of how to reconcile, in the minds of our voters, the grand declarations issued at summit meetings of the Heads of Government with the reality of day Notional reserve for officials seconded in the interests of the service not included in the grand total. It's a grand occasion... for them. We heard you're celebrating a grand occasion today.	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

IN THE GRAND OCCASION.

149,200 results on the web

AT THE GRAND OCCASION.

1109,000 results on the web

More popular!

day politics.
Today's meeting is a grand occasion.
to
Notional reserve for officials seconded in the interests of the service not included in the grand total.
As MEPs, we have been confronted on several occasions recently with the problem of how to reconcile, in the minds of our voters, the grand declarations issued at summit meetings of the Heads of Government with the reality of day
Notional reserve for officials seconded in the interests of the service not included in the grand total.
It's a grand occasion... for them.
We heard you're celebrating a grand occasion today.

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.