The trick here is cooking the barley ahead of time so that all you have to do is assemble the dish and pop in the microwave.
Spoon cooked barley evenly into the bottom of a microwave-safe, 9-inch deep-dish pie plate (or similar casserole dish). Spread half of the onion slices evenly over the barley. Layer the eggplant slices to cover the barley completely.
Drizzle eggplant & rice mixture with the olive oil, then sprinkle the Garlic & Herb blend over the top. Spread the remaining onion slices over the top of the eggplant. Cover with a microwave-safe cover and cook on HIGH about 12 minutes (the eggplant should be soft and cooked throughout).
Layer the sliced or shredded cheese over the top and cook on HIGH, covered or uncovered, for exactly 1 minute longer (just until cheese is nicely melted).