There are lots of little rodeos around the state throughout the Summer months.
In Vale they hold their annual rodeo on the 4th of July as part of the annual celebration for independence. This makes it a bit more special in my mind and all the more fun.
If you've never been to a small town rodeo then you are really missing out on a bit of American heritage that I recommend you reconcile immediately, if not sooner. Authentic cowboys (you know the kind that actually raise cows and make a living from it) are to be found in these small towns mingling with the rodeo cowboys. Locals as well as traveling vendors offer a variaty of curios that can only be found in these small town events, and the food can never be beat.
If you travel to a summer rodeo in Vale, or any part of Eastern Oregon then I have to recommend a couple of things. First, bring plenty of sunscreen. Summer in the high desert is hot! Expect it to be hot and dry and you can't enjoy much of anything with a sunburn. Also bring plenty of water especially for kids and pets. Dehydration and sun stroke or heat sickness are real possibilities. Finally, don't stray too far off the beaten path without doing some research. There are a lot of trails and it easy easy to get lost, not to mention that lat summer tends to be snake season and the rattlers in the sage brush covered hills aren't terribly friendly.