How to counter Orianna
Let us take a look on how to beat Orianna. We will look at champions who are strong against Orianna and who are weak against Orianna. Use win rate, gold difference and creep score difference at minute 10 to find the best 
Mid champion who counters Orianna. You can already win in champion select with the right counters for Orianna. If you want to know how to counter Orianna then you need to take into account the best picks vs Orianna and the worst picks vs Orianna. This Orianna counter data is based on matches played by Pros on patch 15.12 and previous ones. It is important to see whether Pros counter picked Orianna or whether they played as Orianna.
Champions used by Pros to counter pick Orianna
Looking at the matches from Pros (see table Pros counter picked Orianna) we can see that they picked 
Viktor most often to counter pick Orianna. The matchup Viktor vs Orianna occured 44 times. Orianna has 25 wins and 19 losses in this matchup. Learn how to counter pick Viktor to get another perspective on the data.
Lane outcome for Orianna
When looking at Orianna counters you will notice that win rates alone are not conclusional. Therefore we provide an overview (see table Lane Outcome) where you can see the lane outcome of Pros who played Orianna. The lane outcome of Orianna consists of three outcomes: Win, Loss or Draw. Let's take a look of Orianna lane and match outcome for specific matchups. Considering the lane outcome and the match outcome of a specific matchup, might enable you to find the right counter for Orianna.
Conclusion
Analyze the available data and learn how to beat Orianna. To master Orianna take also a look on Orianna builds and runes for Orianna. Good luck, Summoner!