While barley cooks, toss spinach in a large mixing bowl. Zest the orange into a smaller bowl (or a lidded jar such as a mason jar or dressing bottle). Then juice the orange to add to zest. Add olive oil, 1/4 tsp salt; mix/shake.
Add cooked, hot barley to the spinach and allow it to wilt. Pour dressing over the spinach and mix to thoroughly coat both spinach and barley.
Slice strawberries and onions, grate (or julienne) carrots, and add to spinach. Toss in lettuce, nuts and cubed cheddar cheese. Season with remaining salt and pepper (fresh ground if you have it!); toss together one more time.