You have to be careful with things like frozen vegetables "in sauce." I was eating dinner with my parents (who had to carefully watch over my diet from since I was 2 years old when I developed celiac disease) and my mother had bought "frozen broccoli with butter sauce" and didn't think to check the ingredients. Luckily, I had an intuition to check the packaging before I ate any; sure enough, the "butter" part contained wheat as a thickener.
The same often goes for meats, fruits and so forth that are "seasoned" or "contain sauce." Hell, stores that sell whole roasted chickens often use modified food starch (which can contain wheat; often it isn't specified) on their chickens. Even sliced lunch meats that look straightforward can contain gluten.
I often tell my friends not to bother trying to make me food or find food that will accommodate me because it's more of a hassle for them. "Well it's just X..." (yogurt, tacos, a rice dish, etc, etc) usually contains a lot more under the surface than it would appear. And somewhere in there, it's likely that something can contain wheat.