I used to live in OC (Anaheim and later Laguna Niguel), although its been a number of years.
In Laguna Niguel, Stix (the "progenator" of the Pick Up Stix chain), has the best Hot and Sour soup I have ever had. I could make a meal just out of that soup and the pot stickers. Mandarin Gourmet in Costa Mesa was also very good.
Typically a recommendation of a chain place isn’t appropriate for forums such as this, but an Orange County original – Claim Jumper – has absolutely huge portions of "All-American" type cooking. There are a number around the county.
Another chain operation with one Orange County location is Maggiano’s Little Italy just outside the South Coast Plaza shopping center. Meals can be eaten family stle, as the portion sizes are huge. Their serving sizes almost rival those served by Buca di Beppo, but IMO, the quality of the pasta sauces at Maggianos is vastly superior to what is served at Buca’s
For Japanese, Taiko in Irvine draws lots of folks, to its fairly informal and casual style dining.